Answer:
a)
revenue = x amount of phones x price
revenue = x(500 - 0.5x)
revenue = 500x - 0.5x²
we find revenue' (derivative):
revenue' = 500 - x
x = 500
the company should sell 500 smartphones to maximize revenue, the selling price = 500 - (0.5 x 500) = $250 per smartphone. Maximum weekly revenue = $250 x 500 = $125,000
b)
profit = revenue - cost
profit = 500x - 0.5x² - 20,000 - 135x
profit = -0.5x² + 365x - 20,000
we must find profit' (derivative):
profit' = -x + 365
x = 365
In order to maximize profits, you have to sell 365 smartphones per week. Maximum weekly profit = -0.5(365²) + 365(365) - 20,000 = -66,612.50 + 133,225 - 20,000 = $46,612.50.
The smartphone's price = 500 - (0.5 x 365) = $317.50