6 1/10 because 3 3/5 equals 3 6/10 and 2 1/2 equals 2 5/10. 3 6/10 plus 2 5/10=6 1/10
The ratio of depth to horizontal distance is the tangent of the angle of depression.
250 +tan(15°)*1500 = 651.9 . . . . . feet
P is at 0,-1
Q is at 2,-1
R is at 2, -2
S is at 0, -2