Measuring & finding temperature

Any & all assistance with this problem is greatly appreciated--I'm at a loss.

Measurements in the copper mines of northern Michigan have determined the geothermal gradient in the upper crust to be approximately 0.025 degrees Celsius/meter.

Determine the temperature at :

A. 2500 meters

B. 5 kilometers

C. 250 kilometers

This is quite simple, solve it with mathematical logic like so:

1 Meter= 0.025 degrees Celsius, so

A. 2500 meters = ?
2500 x 0.025= 62.5 degrees Celsius

in the other questions, make the kilometers into metres:

B. 5 km= 5000 meters
5000 x 0.025= 125 degrees Celsius

C. 250 km= 250000 meters
250000 x 0.025= 6250 degrees Celsius

A. 0.025 x 2500 = 62.5 so the temperature is about 63°C warmer than at the surface.

B. 5 km = 5000 m
0.025 x 5000 = 125 so the temperature is about 125°C warmer than at the surface.

C. Is the crust that thick in Michigan?? The copper mines certainly aren't so any calculation would be an unreasonable extrapolation.