Area for grazing by the goat tied to a silo

Problem
A goat is tied outside a silo of radius 10 m by a rope just long enough for the goat to reach the opposite side of the silo. Find the area available for grazing by the goat. Note that the goat may not enter the silo.
A. 1033.54 m2
B. 2067.08 m2
C. 516.77 m2
D. 2583.86 m2
 

Solution