A shade of green paint is made by mixing blue paint and yellow paint in the ratio of 4 to 3. How many pints of blue paint and yellow paint are needed to make 21 pints of the green paint? A. 12 pints of blue paint and 3 pints of yellow paint B. 9 pints of blue paint and 12 pints of yellow paint C. 16 pints of blue paint and 9 pints of yellow paint D. 12 pints of blue paint and 9 pints of yellow paint