I believe the question is a bit ambiguous.

First of all we are talking about ONLY year 2008 NOT all the curve and its changing over time

However, the stem says

If half of the customers who switched to Company A

usually, this means that we had a number X and the new number is Y so the difference is the number of customers who went from B to A

But the question accounts for ONLy the end value , which is 4

The pie chart shows the breakdown of profit from the various plans offered and indicates that 25 percent of the profit came from Plan X.
Plan X accounts for 25 percent of $220 million 5 $55 million. Half of $55 million is $27.5 million.

Divide $27.5 by 2 : $27.5 / 2 = $13.75. The correct choice is (B)

from the graph. half of 4 = 2

220 * 0.125 / 2

ans:B
total 220M from second graph, plan x= 25% so half profit 25/2=12.5%, so it profit .125 x 220/(2 million )= 13.75