To find the measure of the s angle que are going use the cosine law because we know all the sides of the triangule:
s² = r² + t² - 2*r*t * cos(S)
Then solve the equation
s² -r² - t² = -2*r*t * cos(S)
arccos ((s² -r² - t² /-2*r*t)) = S
arccos (((250)² -(850 cm)²-(940 cm)² /(-2* 850 cm*940 cm) = S
14.9 = S
round to the nearest 10th of a degree
15º = S