Solve the Problem $x$ Graphing Calculators Is Figured to Be $x ( 21 - 0.2 x )$

Multiple Choice

Solve the problem.
-The revenue achieved by selling $x$ graphing calculators is figured to be $x ( 21 - 0.2 x )$ dollars. The cost of each calculator is $\$ 13$ . How many graphing calculators must be sold to make a profit (revenue - cost) of at least $\$ 72.80$ ?

A) between 14 and 26 calculators
B) between 4 and 16 calculators
C) between 15 and 13 calculators
D) between 16 and 24 calculators