Answer
a. $f(x)=300+0.7x$
b. $g(x)=40+0.9x$
c. $1300$ dollars, $1210$ dollars.
Work Step by Step
a. For plan A, the annual price is $f(x)=300+0.7x$ where $x$ is the dollars of merchandise purchased.
b. For plan B, the annual price is $g(x)=40+0.9x$ where $x$ is the dollars of merchandise purchased.
c. Let the above cost to be equal, we have $300+0.7x=40+0.9x$ which gives $0.2x=260$ and $x=1300$ dollars. The total would be $f(1300)=300+0.7(1300)=1210$ dollars.
