Answer:
27000 Nm
Explanation:
The boom end at A is fixed and end at B is subjected to a 3kN force. Boom AB has length of 9m. The moment about A is the product of force 3kN (3000 N) at B and the moment arm of 9m
M = FL = 3000 * 9 = 27000 Nm
So the moment about A is 27000 Nm