Isosceles triangles T and T^{\prime} are not congruent but have the same area and the same perimeter. The sides of T have lengths of 5,5 , and 8 , while those of T^{\prime} have lengths a, a, and b. Which of the following numbers is closest to b ?
Answer Choices
A. 3
B. 4
C. 5
D. 6
E. 8