the profit of the company is
[tex]p(x)=-0.5x^2+85x-45x-300=-0.5x^2+40x-300[/tex]for part B we get
[tex]\begin{gathered} -0.5x^2+40x-300=50\rightarrow \\ 0.5x^2-40x+350=0 \\ x^2-80x+700=0 \\ (x-10)(x-70)=0 \\ x=10,x=70 \end{gathered}[/tex]so, to make a profit of $50 the compay have to sell 10 or 70 units
for part c we get
[tex]\begin{gathered} -0.5x^2+40x-300=2500\rightarrow \\ 0.5x^2-40x+2800=0 \\ x^2-80x+5600=0\text{ } \\ \text{ using the general formula we get that} \\ 80^2-4\cdot1\cdot5600<0\text{ so it is impossible to make a profit of 2500} \end{gathered}[/tex]