Given That a Region Has an Average Annual Air Temperature $\circ$

Given that a region has an average annual air temperature of 13 ^$\circ$ C,what would the subsurface temperature be at a depth of 2 km? Assume the geothermal gradient is the same as the world average geothermal gradient,which is approximately 30 ^$\circ$ C per kilometer.

A) 60 ^$\circ$ C
B) 73 ^$\circ$ C
C) 80 ^$\circ$ C
D) 93 ^$\circ$ C