ΔABC is a right triangle. ΔA'B'C' has a hypotenuse of 10 after ΔABC undergoes a dilation by a factor of 2. If ΔABC has a short leg of 5 - x and a long leg of 2x, what is the length of the short leg of ΔABC? A) 2 B) 3 C) 5 D) 7