Answer:
70 units
Step-by-step explanation:
The computation of profit maximizing output level is shown below:-
Monopolist perform Marginal Revenue which equivalent to the Marginal Cost as
MR = Marginal Revenue and MC = Marginal Cost
MR = 320 - Q
Now we will find the MC which is
now we will put the value of which is into MR = MC
320 - Q = 3Q + 40
280 = 4Q
70 = Q
So, the profit maximizing output level is 70 units.