Solve the Problem $\mathrm { P } _ { 1 }$

Solve the problem.
-An airline with two types of airplanes, $\mathrm { P } _ { 1 }$ and $\mathrm { P } _ { 2 }$ , has contracted with a tour group to provide transportation for a minimum of 400 first class, 900 tourist class, and 1500 economy class passengers. For a certain trip, airplane $\mathrm { P } _ { 1 }$ costs $\$ 10,000$ to operate and can accommodate 20 first class, 50 tourist class, and 110 economy class passengers. Airplane $\mathrm { P } _ { 2 }$ costs $\$ 8500$ to operate and can accommodate 18 first class, 30 tourist class, and 44 economy class passengers. How many of each type of airplane should be used in order to minimize the operating cost?

A) $9 \mathrm { P } _ { 1 }$ planes and $13 \mathrm { P } _ { 2 }$ planes
B) $14 \mathrm { P } _ { 1 }$ planes and $7 \mathrm { P } _ { 2 }$ planes
C) $5 \mathrm { P } _ { 1 }$ planes and $22 \mathrm { P } _ { 2 }$ planes
D) $13 \mathrm { P } _ { 1 }$ planes and $9 \mathrm { P } _ { 2 }$ planes