To Find the Distance Across a River a Surveyor Chooses $A$

Essay

To find the distance across a river a surveyor chooses points $A$ and $B$ , $50$ m apart and a reference point $\mathrm { C }$ on the other side of the river. Approximate the distance, $b$ , between $A$ and $\mathrm { C }$ given that $\angle A = 54 ^ { \circ }$ and $\angle B = 77 ^ { \circ }$ .