I need help with these two questions. thanks in advance! show steps!

In the figure, the dashed line extending from the force vector is called the line of action of F_vec. The perpendicular distance r_m from the pivot point p to the line of action is called the moment arm of the force.

a.) What is the length, r_m, of the moment arm of the force F_vec about point p? Express in r and theta

b.) Find the torque about p due to F_vec. Your answer should correctly express both the magnitude and sign of torque.

Express in terms of r_m and F or in terms of r, theta, and F.

The questions are with this picture: