Ralph went to the store and bought 12 pairs of socks for a total of \$ 24. Some of the socks he bought cost \$ 1 a pair, some of the socks he bought cost \$ 3 a pair, and some of the socks he bought cost \$ 4 a pair. If he bought at least one pair of each type, how many pairs of \$ 1 socks did Ralph buy?
Answer Choices
A. 4
B. 5
C. 6
D. 7
E. 8