The altitude of a plane above sea level, in feet, m minutes after departure is 293 + 500m. Which statement is correct?
A.
The plane's altitude increases by 500 feet each minute after departure.

B.
The plane's altitude decreases by 500 feet each minute after departure.

C.
The plane's altitude increases by 293 feet each minute after departure.

D.
The plane's altitude decreases by 293 feet each minute after departure.