Performance Stock Units: In January 2017, Altria Group, Inc.  granted an aggregate of 187,886 performance stock units to eligible employees.
The payout of the performance stock units requires the achievement of certain performance measures, which were predetermined at the time of grant, over a three-year performance cycle.
These performance measures consist of Altria Group, Inc. ’s adjusted diluted earnings per share (“EPS”) compounded annual growth rate and Altria Group, Inc. ’s total shareholder return relative to a predetermined peer group.
The performance stock units are also subject to forfeiture if certain employment conditions are not met.
At December 31, 2017, Altria Group, Inc.  had 170,755 performance stock units remaining, with a weighted-average grant date fair value of $70.39 per performance stock unit.
The fair value of the performance stock units at the date of grant, net of estimated forfeitures, is amortized to expense over the performance period.
Altria Group, Inc.  recorded pre-tax compensation expense related to performance stock units for the year ended December 31, 2017 of $6 million.
The unamortized compensation expense related to Altria Group, Inc. ’s performance stock units was $7 million at December 31, 2017.
Altria Group, Inc.  did not grant any performance stock units during 2016 and 2015.
Note 12.
Earnings per Share Basic and diluted EPS were calculated using the following:
## Table 0 ##
Notes to Financial Statements 146 Southern Company 2017 Annual Report Power Company, for purposes of these definitions, debt excludes any project debt incurred by certain subsidiaries of Southern Power Company to the extent such debt is non-recourse to Southern Power Company and capitalization excludes the capital stock or other equity attributable to such subsidiaries.
At December 31, 2017, Southern Company, the traditional electric operating companies, Southern Power Company, Southern Company Gas, and Nicor Gas were each in compliance with their respective debt limit covenants.
A portion of the $8.1 billion unused credit with banks is allocated to provide liquidity support to the revenue bonds of the traditional electric operating companies and the commercial paper programs of Southern Company, the traditional electric operating companies, Southern Power Company, Southern Company Gas, and Nicor Gas.
The amount of variable rate revenue bonds of the traditional electric operating companies outstanding requiring liquidity support as of December 31, 2017 was approximately $1.5 billion as compared to $1.9 billion at December 31, 2016.
In addition, at December 31, 2017, the traditional electric operating companies had approximately $714 million of revenue bonds outstanding that were required to be remarketed within the next 12 months.
Subsequent to December 31, 2017, $50 million of these revenue bonds of Mississippi Power which were in a long-term interest rate mode were remarketed in an index rate mode.
Southern Company, the traditional electric operating companies (other than Mississippi Power), Southern Power Company, Southern Company Gas, and Nicor Gas make short-term borrowings primarily through commercial paper programs that have the liquidity support of the committed bank credit arrangements described above.
Commercial paper and short-term bank term loans are included in notes payable in the balance sheets.
Details of short-term borrowings were as follows:
## Table 1 ##
In addition to the short-term borrowings of Southern Power Company included in the table above, at December 31, 2016, Southern Power Company subsidiaries had credit agreements (Project Credit Facilities) assumed with the acquisition of certain solar facilities, which were non-recourse to Southern Power Company, the proceeds of which were used to finance project costs related to such solar facilities.
The Project Credit Facilities were fully repaid in January 2017 and had total amounts outstanding of $209 million at a weighted average interest rate of 2.1% at December 31, 2016.
Redeemable Preferred Stock of Subsidiaries At December 31, 2016, each of the traditional electric operating companies had outstanding preferred and/or preference stock.
During 2017, Alabama Power and Gulf Power each redeemed all of its outstanding preference stock and Georgia Power redeemed all of its outstanding preferred and preference stock.
The preferred stock of Alabama Power and Mississippi Power contains a feature that allows the holders to elect a majority of such subsidiary’s board of directors if preferred dividends are not paid for four consecutive quarters.
Because such a potential redemption-triggering event is not solely within the control of Alabama Power and Mississippi Power, this preferred stock is presented as “Redeemable Preferred Stock of Subsidiaries” in a manner consistent with temporary equity under applicable accounting standards.
The preferred and preference stock at Georgia Power and the preference stock at Alabama Power and Gulf Power did not contain such a provision.
As a result, under applicable accounting standards, the preferred and preference stock at Georgia Power and the preference stock at Alabama Power and Gulf Power are presented as “Preferred and Preference Stock of Subsidiaries,” a separate component of “Stockholders’ Equity,” on Southern Company’s balance sheets, statements of capitalization, and statements of stockholders’ equity.
Notes to Financial Statements Southern Company 2017 Annual Report 149 compensation granted to employees includes restricted stock units in addition to performance share units.
Prior to 2015, stock-based compensation also included stock options.
As of December?31, 2017, there were 5,112 current and former employees participating in the stock option, performance share unit, and restricted stock unit programs.
In conjunction with the Merger, stock-based compensation in the form of Southern Company restricted stock and performance share units was also granted to certain executives of Southern Company Gas through the Southern Company Omnibus Incentive Compensation Plan.
Performance Share Units Performance share units granted to employees vest at the end of a three-year performance period.
All unvested performance share units vest immediately upon a change in control where Southern Company is not the surviving corporation.
Shares of Southern Company common stock are delivered to employees at the end of the performance period with the number of shares issued ranging from 0% to 200% of the target number of performance share units granted, based on achievement of the performance goals established by the Compensation Committee of the Southern Company Board of Directors.
Southern Company issues performance share units with performance goals based on three performance goals to employees.
These include performance share units with performance goals based on the total shareholder return (TSR) for Southern Company common stock during the three-year performance period as compared to a group of industry peers, performance share units with performance goals based on Southern Company's cumulative earnings per share (EPS) over the performance period, and performance share units with performance goals based on Southern Company's equity-weighted ROE over the performance period.
In 2015 and 2016, the EPS-based and ROE-based awards each represented 25% of the total target grant date fair value of the performance share unit awards granted.
The remaining 50% of the total target grant date fair value consisted of TSR-based awards.
Beginning in 2017, the total target grant date fair value of the stock compensation awards granted was comprised 20% each of EPS-based awards and ROE-based awards and 30% each of TSR-based awards and restricted stock units.
The fair value of TSR-based performance share unit awards is determined as of the grant date using a Monte Carlo simulation model to estimate the TSR of Southern Company's common stock among the industry peers over the performance period.
Southern Company recognizes compensation expense on a straight-line basis over the three-year performance period without remeasurement.
The fair values of the EPS-based awards and the ROE-based awards are based on the closing stock price of Southern Company common stock on the date of the grant.
Compensation expense for the EPS-based and ROE-based awards is generally recognized ratably over the three-year performance period initially assuming a 100% payout at the end of the performance period.
Employees become immediately vested in the TSR-based performance share units, along with the EPS-based and ROE-based awards, upon retirement.
As a result, compensation expense for employees that are retirement eligible at the grant date is recognized immediately while compensation expense for employees that become retirement eligible during the vesting period is recognized over the period from grant date to the date of retirement eligibility.
The expected payout related to the EPS-based and ROE-based awards is reevaluated annually with expense recognized to date increased or decreased based on the number of shares currently expected to be issued.
Unlike the TSR-based awards, the compensation expense ultimately recognized for the EPS-based awards and the ROE-based awards will be based on the actual number of shares issued at the end of the performance period.
In determining the fair value of the TSR-based awards issued to employees, the expected volatility is based on the historical volatility of Southern Company's stock over a period equal to the performance period.
The risk-free rate is based on the U. S.  Treasury yield curve in effect at the time of grant that covers the performance period of the awards.
The following table shows the assumptions used in the pricing model and the weighted average grant-date fair value of performance share award units granted:
## Table 2 ##
The weighted average grant-date fair value of both EPS-based and ROE-based performance share units granted during 2017, 2016, and 2015 was $49.21, $48.87, and $47.75, respectively.
Total unvested performance share units outstanding as of December?31, 2016 were 3.2 million.
During 2017, 1.2 million performance share units were granted and 1.5 million performance share units were vested or forfeited, resulting in 2.9 million unvested performance share units outstanding at December?31, 2017.
The number of shares to be issued for the three-year performance and vesting period ended December?31, 2017 will be determined in the first quarter 2018.
Notes to Financial Statements 154 Southern Company 2017 Annual Report As of December 31, 2016, assets and liabilities measured at fair value on a recurring basis during the period, together with their associated level of the fair value hierarchy, were as follows:
## Table 3 ##
(a) Energy-related derivatives exclude $4 million associated with certain weather derivatives accounted for based on intrinsic value rather than fair value.
(b) Energy-related derivatives exclude cash collateral of $62 million.
(c) Includes the investment securities pledged to creditors and collateral received, and excludes receivables related to investment income, pending investment sales, currencies, and payables related to pending investment purchases and the securities lending program.
See Note 1 under “Nuclear Decommissioning” for additional information.
Valuation Methodologies The energy-related derivatives primarily consist of exchange-traded and over-the-counter financial products for natural gas and physical power products, including, from time to time, basis swaps.
These are standard products used within the energy industry and are valued using the market approach.
The inputs used are mainly from observable market sources, such as forward natural gas prices, power prices, implied volatility, and overnight index swap interest rates.
Interest rate derivatives are also standard over-the-counter products that are valued using observable market data and assumptions commonly used by market participants.
The fair value of interest rate derivatives reflects the net present value of expected payments and receipts under the swap agreement based on the market’s expectation of future interest rates.
Additional inputs to the net present value calculation may include the contract terms, counterparty credit risk, and occasionally, implied volatility of interest rate options.
The fair value of cross-currency swaps reflects the net present value of expected payments and receipts under the swap agreement based on the market’s expectation of future foreign currency exchange rates.
Additional inputs to the net present value calculation may include the contract terms, counterparty credit risk, and discount rates.
The interest rate derivatives and cross-currency swaps are categorized as Level 2 under Fair Value Measurements as these inputs are based on observable data and valuations of similar instruments.
See Note 11 for additional information on how these derivatives are used.
The NRC requires licensees of commissioned nuclear power reactors to establish a plan for providing reasonable assurance of funds for future decommissioning.
For fair value measurements of the investments within the nuclear decommissioning trusts, external pricing vendors are designated for each asset class with each security specifically assigned a primary pricing source.
For investments held within

Tables referenced above, in order (Table 0 first):
<table><tr><td></td><td>For the Years Ended December 31,</td></tr><tr><td>(in millions)</td><td>2017</td><td>2016</td><td>2015</td></tr><tr><td>Net earnings attributable to Altria Group, Inc.</td><td>$10,222</td><td>$14,239</td><td>$5,241</td></tr><tr><td>Less: Distributed and undistributed earnings attributable to share-based awards</td><td>-14</td><td>-24</td><td>-10</td></tr><tr><td>Earnings for basic and diluted EPS</td><td>$10,208</td><td>$14,215</td><td>$5,231</td></tr><tr><td>Weighted-average shares for basic and diluted EPS</td><td>1,921</td><td>1,952</td><td>1,961</td></tr></table>
<table><tr><td></td><td colspan="2">Short-term Debt at the End of the Period</td></tr><tr><td></td><td>AmountOutstanding (in millions)</td><td>Weighted AverageInterest Rate</td></tr><tr><td>December 31, 2017:</td><td></td><td></td></tr><tr><td>Commercial paper</td><td>$1,832</td><td>1.8%</td></tr><tr><td>Short-term bank debt</td><td>607</td><td>2.3%</td></tr><tr><td>Total</td><td>$2,439</td><td>1.9%</td></tr><tr><td>December 31, 2016:</td><td></td><td></td></tr><tr><td>Commercial paper</td><td>$1,909</td><td>1.1%</td></tr><tr><td>Short-term bank debt</td><td>123</td><td>1.7%</td></tr><tr><td>Total</td><td>$2,032</td><td>1.1%</td></tr></table>
<table><tr><td>Year Ended December 31</td><td>2017</td><td>2016</td><td>2015</td></tr><tr><td>Expected volatility</td><td>15.6%</td><td>15.0%</td><td>12.9%</td></tr><tr><td>Expected term(in years)</td><td>3</td><td>3</td><td>3</td></tr><tr><td>Interest rate</td><td>1.4%</td><td>0.8%</td><td>1.0%</td></tr><tr><td>Weighted average grant-date fair value</td><td>$49.08</td><td>$45.06</td><td>$46.38</td></tr></table>
<table><tr><td></td><td colspan="4">Fair Value Measurements Using</td><td></td></tr><tr><td>As of December 31, 2016:</td><td>Quoted Prices in Active Markets for Identical Assets (Level 1)</td><td>Significant Other Observable Inputs (Level 2)</td><td>Significant Unobservable Inputs (Level 3)</td><td>Net Asset Value as a Practical Expedient (NAV)</td><td>Total</td></tr><tr><td></td><td colspan="5">(in millions)</td></tr><tr><td>Assets:</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Energy-related derivatives<sup>(a)(b)</sup></td><td>$338</td><td>$333</td><td>$—</td><td>$—</td><td>$671</td></tr><tr><td>Interest rate derivatives</td><td>—</td><td>14</td><td>—</td><td>—</td><td>14</td></tr><tr><td>Nuclear decommissioning trusts:<sup>(c)</sup></td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Domestic equity</td><td>589</td><td>73</td><td>—</td><td>—</td><td>662</td></tr><tr><td>Foreign equity</td><td>48</td><td>168</td><td>—</td><td>—</td><td>216</td></tr><tr><td>U.S. Treasury and government agency securities</td><td>—</td><td>92</td><td>—</td><td>—</td><td>92</td></tr><tr><td>Municipal bonds</td><td>—</td><td>73</td><td>—</td><td>—</td><td>73</td></tr><tr><td>Corporate bonds</td><td>22</td><td>310</td><td>—</td><td>—</td><td>332</td></tr><tr><td>Mortgage and asset backed securities</td><td>—</td><td>183</td><td>—</td><td>—</td><td>183</td></tr><tr><td>Private equity</td><td>—</td><td>—</td><td>—</td><td>20</td><td>20</td></tr><tr><td>Other</td><td>11</td><td>15</td><td>—</td><td>—</td><td>26</td></tr><tr><td>Cash equivalents</td><td>1,172</td><td>—</td><td>—</td><td>—</td><td>1,172</td></tr><tr><td>Other investments</td><td>9</td><td>—</td><td>1</td><td>—</td><td>10</td></tr><tr><td>Total</td><td>$2,189</td><td>$1,261</td><td>$1</td><td>$20</td><td>$3,471</td></tr><tr><td>Liabilities:</td><td></td><td></td><td></td><td></td><td></td></tr><tr><td>Energy-related derivatives<sup>(a)(b)</sup></td><td>$345</td><td>$285</td><td>$—</td><td>$—</td><td>$630</td></tr><tr><td>Interest rate derivatives</td><td>—</td><td>29</td><td>—</td><td>—</td><td>29</td></tr><tr><td>Foreign currency derivatives</td><td>—</td><td>58</td><td>—</td><td>—</td><td>58</td></tr><tr><td>Contingent consideration</td><td>—</td><td>—</td><td>18</td><td>—</td><td>18</td></tr><tr><td>Total</td><td>$345</td><td>$372</td><td>$18</td><td>$—</td><td>$735</td></tr></table>

Question: What's the average of the Weighted average grant-date fair value in the years where Commercial paper for AmountOutstanding (in millions) is positive?
Answer: 47.07
Reasoning program: add(49.08,45.06), divide(#0,2)