Final answer:
The limit price to deter entry into the market is $39, as this is where the incumbent firm earns zero economic profit, which does not attract new entrants.
Step-by-step explanation:
Calculating the Limit Price to Deter Entry
To calculate the limit price that will deter entry into a market, we will examine the demand curve D(P) = Q = 80 - P and the cost function C(Q) = 64 - 2Q. The limit price is where economic profits are zero, thus deterring entry because new entrants would not expect to make a profit. First, we set the marginal revenue (MR) equal to marginal cost (MC) to find the profit-maximizing quantity Q*. The demand curve can be written as P = 80 - Q, so the marginal revenue for this linear demand curve would be MR = 80 - 2Q. The marginal cost from the cost function is MC = dC/dQ = -2. Setting MR equal to MC gives us:
80 - 2Q = -2
This implies Q* = 41. To find the corresponding price, we substitute Q* back into the demand equation:
P = 80 - Q*
P = 80 - 41 = 39
This price of $39 is the limit price, the highest price the incumbent can charge without attracting new entrants, assuming costs are the same for all firms.