Answer:
The sales must grow in 1125 units
Consider:
Price: $80
Variable costs: $45
Total fixed costs: $80.000
Sales level: 2500
Marketing expense: $90.000
Total revenue $200.000
(-)Variable costs $ 112.500
(-)Total fixed costs $ 80.000
______________________________
Profit $ 7.500
Marketing expense: $90.000 /$80 price=1125 units