An industry has 200 firms, each with the production functionf(x1,x2) =x₁^1/2x₂^1/2. The price of factor 1 is $1 and the price of factor 2 is $1. In the long run, both factors are variable, but in the short run, each firm is stuck with using 10 units of factor 2. The long- run industry supply curve is

a. upward sloping with zero supply if price is less than $10.

b. horizontal with zero supply for prices less than $2 and infinite supply for prices greater than $2.

c. horizontal with zero supply for prices less than $5 and infinite supply for prices greater than $5.

d. downward sloping for outputs less than 10.

e. None of the above