Above is a GMAT Prep Test Question, which I thought I understood and solved correctly, but apparently not. My answer was C) $140, the correct answer is D) $160.

My reasoning was...

Costs = 600 units x $90 cost ea = $36,000 cost
Profits = Revenue - Costs, thus Revenue = Profits ($42k min goal) + Costs ($36k)
Revenue = $78k min

$78k / 600 units = $130 min sell price, to have $42k profits.
Closest answer choice C) $140

correction: 600 * 90 = $54,000

(54000 + 42000)/600 = $160