A Firm Has the Production Function F(x, Y)= 60x ^4/5

Multiple Choice

A firm has the production function f(x, y) = 60x ^4/5 y^1/5.The slope of the firm's isoquant at the point (x, y) = (40, 80) is (pick the closest one)

A) -0.50.
B) -4.
C) -0.25.
D) -8.
E) -0.25