The positions of point A on the building and point B on the antenna have been measured

Question:

The positions of point A on the building and point B on the antenna have been measured relative to the electronic distance meter (EDM) at O. Determine the distance between A and B. Hint: Formulate a position vector directed from A to B; then determine its magnitude.

Given:
a = 460 m
b = 653 m
α = 60 deg
β = 55 deg
θ = 30 deg
φ = 40 deg