Let x = number of pumps sold
Revenue = (price)(quantity) = 9x
Cost = fixed cost + variable costs = 50000 + 0.20(9x)
= 50000 + 1.8x
The company breaks even when revenue = cost
9x = 50000 + 1.8x
7.2x = 50000
x = 6944.444 ≈ 6944 bicycle pumps