Answer:
$30,000,000
Explanation:
compensation expense = total number of stocks granted x grant date value = 6,000,000 x $15 = $90,000,000
this expense will be allocated proportionally during the vesting period = $90,000,000 / 3 years = $30,000,000 per year
compensation expense per year (2016, 2017, 2018) = $30,000,000