Answer: $403 per calculator
Step-by-step explanation:
Assume the selling price is x. 
400 calculators. 
Upgrading them would cost $150,000 but if sold in present condition would fetch $11,200.
Expression would be;
400x - 150,000 = 11,200
400x = 161,200
x = 161,200/400
x = $403 per calculator