Fifteen percent of the pigment in paint color A is black. Sixty percent of the pigment in paint color B is black. An unknown amount of paint color B is mixed with 40 ml of paint color A, resulting in a paint that contains 25% black pigment. Which equation can be used to solve for x, the total amount of paint in the mixture of the two colors?

A. 0.15(40) + 0.6x = 0.25(40 + x)
B. 0.15(40) + 0.6(x – 40) = 0.25(x)
C. 0.15(40) + 0.6x = 0.25(40 – x)
D. 0.15(40) + 0.6(x + 40) = 0.25(x)