Total profit earned:
[tex]\begin{gathered} Pi(q)=R(q)-C(q) \\ \\ Pi(q)=600q-q^2-75-6q \\ Pi(q)=-q^2+594q-75 \\ \end{gathered}[/tex]Profit Maximizing Quantity:
1-Determine marginal revenue by taking the derivative of total revenue
[tex]\frac{d}{dq}R(q)=600-2q[/tex]2-Determine marginal cost by taking the derivative of total cost
[tex]\frac{d}{dq}C(q)=6[/tex]3-Set marginal revenue equal to marginal cost and solve for q
[tex]\begin{gathered} 600-2q=6 \\ \\ \text{Subtract 600 in both sides of the equation:} \\ 600-600-2q=6-600 \\ -2q=-594 \\ \\ \text{Divide both sides of the equation into -2}\colon \\ \frac{-2}{-2}q=\frac{-594}{-2} \\ \\ q=297 \end{gathered}[/tex]Then, the profit maximizing quantity is 297