Moments in Engineering Mechanics?

Question

http://highered.mcgraw-hill.com/tbern/public_html/0072976985/chap3/sect0/prob8/q.html

in the previous picture:

an athlete is exercising while wearing a 5 lb weigh at his ankle (A)

determine the moment of the weight about the knee joint at B

there are other unknowns but I don't need them just this part which I need

Answer 1

It's 14" from his knee joint measured along a line at 15 deg to the horizontal. Just look for the horizontal lever arm L, since the weight w is a vertical force.
moment = wL = 5*14cos(15deg) inch-lb