Answer:

Explanation:
The torque of a force is given by:

where
F is the magnitude of the force
d is the distance between the point of application of the force and the centre of rotation of the system
 is the angle between the direction of the force and d
 is the angle between the direction of the force and d
In this problem, we have:
 , the force
, the force
 , the distance of application of the force from the centre (0,0)
, the distance of application of the force from the centre (0,0)
 , the angle between the direction of the force and a
, the angle between the direction of the force and a
Therefore, the torque is
