Answer:
The profits will be "24.5".
Explanation:
As we know,
Monopoly Power, [tex]MC=\frac{dC(q)}{dq}[/tex]
                   [tex]=11[/tex]
Withe either two-part tariff,
P = MC
and,
Profit = CS (Costumer surplus)
Now,
[tex]p=18-q=11[/tex]
and, [tex]q = 7[/tex]
When,
q = 0 and p = 18
Profit = [tex](\frac{1}{2})\times (18-11)\times 7[/tex]
⇒    = [tex]\frac{1}{2}\times 7\times 7[/tex]
⇒    = [tex]\frac{1}{2}\times 49[/tex]
⇒    = [tex]24.5[/tex]