Use the law of sines to find the length of side c.
C
be
41.59
37
42°
А
С
CD
O A. 36.64
B. 54.94
C. 37
37 36

Without the calculator let's just estimate that .5/42 = 1.2% change in the angle; we reduce the length a=37 by 1.2% to get 37×.988=36.556.  That's probably good enough to choose A.

Let's do it the way they want.

A

Estimate worked.  Sine is approximately linear when the range is small enough.    

b.-4 units

all you   do is count how many times you move