Use the figure shown.

There is a solid triangle ACB in which D is the point on the side AB. The length of side AC is labeled as b, the length of side CB is labeled as a, and the length of side AB is 24. A dashed segment CD is formed by the point A and point D having length 5.

D is the midpoint of AB¯¯¯¯¯¯¯¯ and m∠ACB=134.76°. What type of triangle is △ACD?

A. right
B. equilateral
C. isosceles
D. obtuse

80 points