Finding increase in percentage difference by comparing two different values of percentages

A and B were hired for the same salary. A got two 40% hikes whereas B got a 90% hike. What is the percentage difference in the hikes thay got?
a. 16%                         b. 6%                           c. 10%             d. 8%

Solution
A => 1.4 X 1.4 = 1.96
B => 1.9     
1.96 -1.9=0.06
=> 6% difference.