Answer
The force on the forearm from the humerus is directed down.
Work Step by Step
Let "up" be the positive direction.
We can consider the vertical forces on the forearm to find the force on the forearm from the humerus $F_h$:
$\sum F_y = 0$
$F_h+1900~N+(15~kg)(9.8~m/s^2)-(2.0~kg)(9.8~m/s^2) = 0$
$F_h = (2.0~kg)(9.8~m/s^2)-1940~N-(15~kg)(9.8~m/s^2)$
$F_h = -2100~N$
The negative sign shows that the force on the forearm from the humerus is directed down.
