Let \triangle A B C be an isosceles triangle with B C=A C and \angle A C B=40^{\circ} Construct the circle with diameter \overline{B C}, and let D and E be the other intersection points of the circle with the sides \overline{A C} and \overline{A B}, respectively. Let F be the intersection of the diagonals of the quadrilateral B C D E. What is the degree measure of \angle B F C ?

**Answer Choices**

A. 90

B. 100

C. 105

D. 110

E. 120