$6$ In Fig. $12-19,$ a $25$ kg block is held in place via a pulley system. The person's upper arm is vertical; the forearm is at angle $=30$ with the horizontal. Forearm and hand together have a mass of $2\mathrm{.}0$ kg $,$ with a center of mass at distance $d_1=15cm$ from the contact point of the forearm bone and the upper$-$arm bone $($humerus$).$ The triceps muscle pulls vertically upward on the forearm at distance $d_2=2\mathrm{.}5cm$ behind that contact point. Distance $d_3$ is $35$ cm $.$ What are the $($a$)$ magnitude and $($b$)$ direction $($up or down$)$ of the force on the forearm from the triceps muscle and the $($c$)$ magnitude and $($d$)$ direction $($up or down$)$ of the force on the forearm from the humerus?

Figure $12-19$ Problem $6.$