The correct answer is 14.2 lb which is choice D.
Let:
F = minimum force required to prevent ball from rolling down the ramp
The formula will be:
F = w * sin theta
F = w * sin (39 degrees)
F = 22.6 * sin (39)
= 14.2 lb (this is rounded to the nearest tenth)
Cross mutiply and the answer would be 13/2 or 6.5