Suppose that firms face the following production function: Q = L^(1/4) + K^(1/4). Then, which of the following is correct based on the conditional labor demand:

a) law of demand holds, labor and capital are substitutes and labor is a normal input

b) law of demand holds, labor and capital are substitutes and labor is an inferior input

c) law of demand holds, labor and capital are complements and labor is neither normal nor an inferior input

d) law of demand holds, labor and capital are substitutes and labor is neither normal nor an inferior input