An Athlete Holds a 7 $\overrightarrow { \mathrm { F } }$

Multiple Choice

An athlete holds a 7.5-kg shot put in his hand with his lower arm horizontal, as shown in the figure. His lower arm has a mass of 2.8 kg and its center of gravity (or center of mass) is 12 cm from the elbow-joint pivot. How much force must the extensor muscle (which is $\overrightarrow { \mathrm { F } }$ _M in the figure) in the upper arm exert on the lower arm?

A) 100 N
B) 500 N
C) 1000 N
D) 1500 N