Determine magnitude and direction?

An object of mass m = 1.00kg is observed to have an acceleration a(arrow) with a magnitude of 10m/s^2 in a direction 60 degrees east of north. The force F2 (which is at 90 degrees) acting on the object has a magnitude of 5.00N and is directed north. Determine the magnitude and direction of the other horizontal force F1 acting on the object.