Consider a Firm That Uses Only Labour and Capital

Consider a firm that uses only labour and capital. At the present use of labour and capital, the MP of labour is two times the MP of capital, and the price of labour is two times the price of capital. In order to minimize its costs, the firm should

A) not alter its present factor mix.
B) decrease capital and increase labour.
C) increase both labour and capital.
D) decrease both capital and labour.
E) substitute capital for labour until their marginal products are equal.