R(4) = 4(30 - 3 * 4) = 4(30 - 12) = 4(18) = $72K (K is used to represent $1000)
When 4000 CD players are produced, the company earns $72,000 in revenue
To determine where the company will maximize revenue, find the derivative of R(x) and set it equal to zero.
R(x)= x(30 - 3x) = 30x - 3x²
R'(x) = 30 - 6x = 0
30 = 6x
x = 5, so when the company produces 5000 CD players, it will maximize its revenue
The amount of revenue will be R(5) = 5(30 - 3 * 5) = 5(30 - 15) = 5(15) = $75K or $75,000