38 2015 ppg annual report and form 10-k notes to the consolidated financial statements 1 . summary of significant accounting policies principles of consolidation the accompanying consolidated financial statements include the accounts of ppg industries , inc . ( 201cppg 201d or the 201ccompany 201d ) and all subsidiaries , both u.s . and non-u.s. , that it controls . ppg owns more than 50% ( 50 % ) of the voting stock of most of the subsidiaries that it controls . for those consolidated subsidiaries in which the company 2019s ownership is less than 100% ( 100 % ) , the outside shareholders 2019 interests are shown as noncontrolling interests . investments in companies in which ppg owns 20% ( 20 % ) to 50% ( 50 % ) of the voting stock and has the ability to exercise significant influence over operating and financial policies of the investee are accounted for using the equity method of accounting . as a result , ppg 2019s share of the earnings or losses of such equity affiliates is included in the accompanying consolidated statement of income and ppg 2019s share of these companies 2019 shareholders 2019 equity is included in 201cinvestments 201d in the accompanying consolidated balance sheet . transactions between ppg and its subsidiaries are eliminated in consolidation . use of estimates in the preparation of financial statements the preparation of financial statements in conformity with u.s . generally accepted accounting principles requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities and the disclosure of contingent assets and liabilities at the date of the financial statements , as well as the reported amounts of income and expenses during the reporting period . such estimates also include the fair value of assets acquired and liabilities assumed resulting from the allocation of the purchase price related to business combinations consummated . actual outcomes could differ from those estimates . revenue recognition the company recognizes revenue when the earnings process is complete . revenue from sales is recognized by all operating segments when goods are shipped and title to inventory and risk of loss passes to the customer or when services have been rendered . shipping and handling costs amounts billed to customers for shipping and handling are reported in 201cnet sales 201d in the accompanying consolidated statement of income . shipping and handling costs incurred by the company for the delivery of goods to customers are included in 201ccost of sales , exclusive of depreciation and amortization 201d in the accompanying consolidated statement of income . selling , general and administrative costs amounts presented as 201cselling , general and administrative 201d in the accompanying consolidated statement of income are comprised of selling , customer service , distribution and advertising costs , as well as the costs of providing corporate- wide functional support in such areas as finance , law , human resources and planning . distribution costs pertain to the movement and storage of finished goods inventory at company- owned and leased warehouses , terminals and other distribution facilities . advertising costs advertising costs are expensed as incurred and totaled $ 324 million , $ 297 million and $ 235 million in 2015 , 2014 and 2013 , respectively . research and development research and development costs , which consist primarily of employee related costs , are charged to expense as incurred. .

2015: research and development 2013 total: 505
less depreciation on research facilities: 19
research and development net: 486
2014: research and development 2013 total: 509
less depreciation on research facilities: 17
research and development net: 492
2013: research and development 2013 total: 479
less depreciation on research facilities: 16
research and development net: 463

legal costs legal costs , primarily include costs associated with acquisition and divestiture transactions , general litigation , environmental regulation compliance , patent and trademark protection and other general corporate purposes , are charged to expense as incurred . foreign currency translation the functional currency of most significant non-u.s . operations is their local currency . assets and liabilities of those operations are translated into u.s . dollars using year-end exchange rates ; income and expenses are translated using the average exchange rates for the reporting period . unrealized foreign currency translation adjustments are deferred in accumulated other comprehensive loss , a separate component of shareholders 2019 equity . cash equivalents cash equivalents are highly liquid investments ( valued at cost , which approximates fair value ) acquired with an original maturity of three months or less . short-term investments short-term investments are highly liquid , high credit quality investments ( valued at cost plus accrued interest ) that have stated maturities of greater than three months to one year . the purchases and sales of these investments are classified as investing activities in the consolidated statement of cash flows . marketable equity securities the company 2019s investment in marketable equity securities is recorded at fair market value and reported in 201cother current assets 201d and 201cinvestments 201d in the accompanying consolidated balance sheet with changes in fair market value recorded in income for those securities designated as trading securities and in other comprehensive income , net of tax , for those designated as available for sale securities. .

Questions:
what is the sum of advertising costs in 2014 and 2015?
what is the sum including advertising costs in 2013?
what is the average cost per year?

Answers:
591
826
275