PERFORMANCE MEASUREMENT-CHASE CO

Good day sir,I was doing this question and i’m confused on how the gross profit figure for yr 4 was calculated.

QUESTION
Sales price will start at $12 per unit for the first two years but then reduce by 5% per annum for each of the next two years.

Gross profit will start at 40% but will reduce as the sales price reduces

The answer
y1 yr 2 yr 3 yr4
Sales (W1) 216,000 237,600 248,292 235,877
Gross profit (W2) 86,400 95,040 91,476 79,061

WORKINGS

(1)Sales Year 1 Year 2 Year 3 Year 4
Sales volume (units) 18,000 1 9,800a 21,780b 21,780

2)Gross profit
Year 1 40% (given) Total gross profit = $216,000 × 0.4 = $86,400
Year 2 40% (given) Total gross profit= $237,600 × 0.4 = $95,040
Year 3 35/95= 36.8421052% Total gross profit = $248,292 × 0.368421052 = $91,476
Year 4* 30.25/90.25= 33.5180055% Total gross profit = $235,877 × 0.335180055 = $79,061

Pls I do not understand how 30.25/90.25 was calculated to get the gross profit figure for yr 4.Thanks