Contribution margin ratio is 40% or $24 per unit
Fixed expenses are $28,800
Variable expense per unit is $36
Assuming Q is quantity, sales needed to achieve monthly net equal to 10% of sales is
Sales = Variable expenses + Fixed expenses + profit
$60Q = $36Q + $28,800 + ($60Q x 10%)
$18Q = $28,800
Q = 1600 units
Monthly sales will have to be 1600 x $60 = $96,000