In Mrs. Williams class there are 13 students. They each have 4 pieces of white paper. Some of the students, s, also have 3 pieces of blue paper each. In all, the students have 64 pieces of paper. Which equation represents this situation?
A. (13 × 3) + s = 64
B. (s × 3) + 13 = 64
C. s × 3 = 64
D. (13 × 4) + (s × 3) = 64