AMC 8 1994 Problem 21

A gumball machine contains $9$ red, $7$ white, and $8$ blue gumballs. The least number of gumballs a person must buy to be sure of getting four gumballs of the same color is $\text{(A)}\ 8 \text{(B)}\ 9 \text{(C)}\ 10 \text{(D)}\ 12 \text{(E)}\ 18$