A Uniform Rod Has a Weight of 40

Multiple Choice

A uniform rod has a weight of 40. N and a length of 1.0 m. It is hinged to a wall (at the left end) , and held in a horizontal position by a vertical massless string (at the right end) , as shown in
What is the magnitude of the torque exerted by the string about a horizontal axis which passes through the hinge and is perpendicular to the rod?

A) 40 m . N
B) 5.0 m . N
C) 30 m . N
D) 20 m . N
E) 10 m . N