I've modified your sketch a little bit. (see attachment)

You've got two right triangles. Use Pythagorean theorem:

Expand the brackets and subtract the first equation from the second one:

Now plug in the given value for b and solve for a. I've got a = 16.9. Thus d = 6.25.

You now have all values to calculate the angles at B.

I asume that you know how to add forces and that you need a parallelogram to get all partial forces.