The price of input X increases by 5%. In response, the quantity of input Y demanded decreases by 2%. We would conclude:

a. that X and Y are complementary inputs and the cross-elasticity of factor demand is equal to -2.50

b. that X and Y are substitute inputs and the cross-elasticity of factor demand is equal to 2.50

c. that X and Y are substitute inputs and the cross-elasticity of factor demand is equal to 0.40

d. that X and Y are complementary inputs and that the cross-elasticity of factor demand is equal to -0.40