Total Profit=Total Revenue - Total Cost
P(x) = R(x)-C(x)
where x is the number of unit sold
From the question,
R(x) = 20x - 0.1x² and c(x) =4x + 2
P(x) = R(x) - c(x) = 20x - 0.1x² - 4x - 2
= -0.1x² + 16x - 2
Profit = -0.1x² + 16x - 2
We have a quadratic equation;
a=-0.1 b= 16
Maximum occurs when x = -b/2a
substitute the values of a and b in the above
x = -16/2(-0.1) = -16/-0.2 = 80
To find the maximum profit, we will substitute x=80 in our profit function
Profit = -0.1(80)² + 16(80) - 2
= -640 + 1280 - 2
= 638
Hence, the maximum profit is $638