please help!! and show explanation

Pastner Brands is a calendar-year firm with operations in several countries. As part of its executive compensation plan, at January 1 2021, the company issued 320,000 executive stock options permitting executives to buy 320,000 shares of Pastner stock for $28 per share. One-fourth of the options vest in each of the next four years beginning at December 31, 2021 (graded vesting). Pastner elects to separate the total award into four groups (or tranches) according to the year in which they vest and measures the compensation cost for each vesting date as a separate award. The fair value of each tranche is estimated at January 1, 2021, as follows: Amount Vesting 25% Vesting Date Dec. 31, 2021 Dec. 31, 2022 Dec. 31, 2023 Dec. 31, 2024 255 Fair Value per Option $5.00 55.be 56.00 $6.40 25 Required: 1. Determine the compensation expense related to the options to be recorded each year 2021-2024, assuming Pastner allocates the compensation cost for each of the four groups (tranches) separately. 2. Determine the compensation expense related to the options to be recorded each year 2021-2024, assuming Pastner uses the straight-line method to allocate the total compensation cost