We are asked to find the Moment about a point in 3-D. And we already know that:

       Moment (M) = distancr(r) x Force(F)                              ......................... (1)

Bold letters represent vector quantities here and 'X' signifies cross product.

Now we are provided with F and two points in space. So to find moment about B. We first find F:

Now F =100 * (Unit Vector QP)

So unit vector QP= $(12i - k)/sqrt(145)$

F= 99.65i - 8.30k

r = PO = (-2i + 3j + 5k)

So M = r x F = (-2i + 3j + 5k) x (99.65i - 8.30k)

                    = ( -24.9i + 481.65j - 298.95k)