A surveyor wishes to measure the width of a trench. He places a transit telescope in a position on one side of the trench that is 18 feet higher than the second location. The surveyor reads the angle of depression from the transit telescope and finds that it is 31°, as shown in the diagram below. If the transit telescope is 4.5 feet above the ground at the first location during this reading, how wide is the trench?

Include all relevant calculations and use the correct units for all measures. Be sure explanations are written in complete sentences.