A weightlifter performing a biceps curl with a $320$ N barbell stops the lifting motion with

his forearms in a horizontal position. The weight of the forearm$/$hand segment is $15$ N$,$

and the COM is located $13$ cm from the elbow.

a$.$ If the line of action of the weight of the barbell is $27$ cm from the axis of rotation

$($elbow joint$),$ what is the magnitude of the moment that the elbow flexors must

exert to maintain that position?

b$.$ If the biceps were the only elbow flexor muscle active $($a rather unlikely event$)$

and its moment arm about the elbow joint was $4\mathrm{.}3$ cm$,$ calculate the biceps muscle

force needed to maintain this equilibrium position. $(5$ pts$)$