Solve the Problem
-An Airplane Is Cruising at an Altitude $21,120 \mathrm{ft}$

Multiple Choice

Solve the problem
-An airplane is cruising at an altitude of $21,120 \mathrm{ft}$ . What is the plane's altitude in miles?

A) $3 \mathrm{mi}$
B) $5 \mathrm{mi}$
C) $4 \mathrm{mi}$
D) $8 \mathrm{mi}$