AMC 8 1986 Problem 16

A bar graph shows the number of hamburgers sold by a fast food chain each season. However, the bar indicating the number sold during the winter is covered by a smudge. If exactly $25\%$ of the chain's hamburgers are sold in the fall, how many million hamburgers are sold in the winter?

$\text{(A)}\ 2.5 \text{(B)}\ 3 \text{(C)}\ 3.5 \text{(D)}\ 4 \text{(E)}\ 4.5$