![a)\$241.68](https://img.qammunity.org/2023/formulas/mathematics/college/xbvcerbuiengj9kzn6nz5dv9du7qz4bhmu.png)
a) To maximize the profit, we'll need to find the Profit function. We know that each item is sold for $10 so the Revenue is R(q)= 10q the profit will be found by subtracting the cost from the Revenue:
![\begin{gathered} C(q)=0.01q^3-0.6q^2+12q \\ R(q)=qx,\Rightarrow R(10)=10q \\ P(q)=10q-(0.01q^3-0.6q^2+12q) \\ P(q)=-0.01q^3+0.6q^2-2q \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/waejnu1gqvy7a1c078dql3co94oxuaktvt.png)
Now, to maximize it we'll need to take the derivative of this Profit function and equate it to zero, applying the power rule like this :
![\begin{gathered} P(q)=-0.01q^3+0.6q^2-2q \\ P^(\prime)(q)=-0.03q^2+1.2q-2 \\ -0.03q^2+1.2q-2=0 \\ -0.03q^2\cdot \:100+1.2q\cdot \:100-2\cdot \:100=0\cdot \:100 \\ -3q^2+120q-200=0 \\ q_=(-120\pm√(120^2-4\left(-3\right)\left(-200\right)))/(2\left(-3\right)) \\ q_1=(10\left(6-√(30)\right))/(3)=1.74 \\ q_2=(10\left(6+√(30)\right))/(3)=38.25 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/41tp2r5eb9ogc4omjtw2gnxtt67avqyndg.png)
Let's take the second derivative test to get to know which are we going to use:
![\begin{gathered} P^(\prime)^(\prime)(q)=-0.06q+1.2 \\ P](https://img.qammunity.org/2023/formulas/mathematics/college/d6nkjhwjudkz9p418y0mpt2svdrboguv3l.png)
So the Maximum profit is obtained if we sell it for 38 units (rounding off to the nearest whole), which yields:
![\begin{gathered} P(38)=-0.01(38)^3+0.6(38)^2-2(38) \\ P(38)=\$241.68 \end{gathered}](https://img.qammunity.org/2023/formulas/mathematics/college/gpiw9if4wbdsck2ewyte898qb8ztw9r9ll.png)