Year Ended June 30,
2019
2018
2017
(in millions)
Included in:
Operating costs
$11.3
$9.9
$11.3
Selling, general and administrative expenses
98.0
86.8
102.8
Total stock-based compensation expense
$109.3
$96.7
$114.1
CII common and preferred units $ — $ — $10.1
$ —
$ —
$10.1
Part A restricted stock units
93.8
82.3
76.5
Part B restricted stock units
13.0
12.4
26.0
Part C restricted stock units
2.5
2.0
1.5
Total stock-based compensation expense
$109.3
$96.7
$114.1

text: (11) STOCK-BASED COMPENSATION
text: The following tables summarize the Company’s stock-based compensation expense for liability and equity classified awards included in the consolidated statements of operations:
text: CII Common and Preferred Units
text: Prior to the Company’s IPO, the Company was given authorization by Communications Infrastructure Investments, LLC (“CII”) to award 625,000,000 of CII’s common units as profits interests to employees, directors, and affiliates of the Company. The common units were historically considered to be stock-based compensation with terms that required the awards to be classified as liabilities due to cash settlement features. The vested portion of the awards was reported as a liability and the fair value was re-measured at each reporting date until the date of settlement, with a corresponding charge (or credit) to stock-based compensation expense. On December 31, 2016, the CII common units became fully vested and as such there is no remaining unrecognized compensation cost associated with CII common units for any period subsequent to December 31, 2016.
text: The value of the CII common units was derived from the value of CII’s investments in the Company and Onvoy, LLC and its subsidiaries (“OVS”), a company that provided voice and managed services which the Company spun off during the year ended June 30, 2014. As the value derived from each of these investments was separately determinable and there was a plan in place to distribute the value associated with the investment in Company shares separate from the value derived from OVS, the two components were accounted for separately. The OVS component of the CII awards was adjusted to fair value each reporting period. On December 31, 2015, CII entered into an agreement to sell OVS to a third party. The sale was completed in May 2016. Based on the sale price, the estimated fair value of OVS awards was increased, resulting in an increase to stock based compensation expense and corresponding increase to additional paid-in capital of $12.9 million for the year ended June 30, 2016. Proceeds from the sale to be distributed to the Company’s employees was paid by CII.

Questions:
question: When did the CII common units become fully vested?
answer: December 31, 2016
question: How many of CII's common units were awarded as profit interests to employees, directors and affiliates of the company?
answer: 625,000,000
question: What does the following table summarize?
answer: The following tables summarize the Company’s stock-based compensation expense for liability and equity classified awards included in the consolidated statements of operations:
question: Which of the years saw a total stock-based compensation expense of more than 100 million?
answer: 2017
2019
derivation: 114.1 > 100 ## 109.3 > 100
question: Which of the years had the highest selling, general and administrative expenses?
answer: 2017
derivation: 102.8 > 98.0 >86.8
question: What were the total operating costs for all 3 years?
answer: 32.5
derivation: 11.3 + 9.9 + 11.3
scale: million