Sid has a job at morgan motors. the salary is $1200 a month, plus 3% of the sales price of every car or truck sid sells (this is called a commission). (a) the total of the sales prices of all the vehicles sid sold during the first month on the job was $72000. what was sid's income (salary plus commission)? (b) in order to make $6000 in a single month, how much selling must sid do? (c) write a linear equation that expresses sid's monthly income y in terms of the value x of the vehicles sid sold. (d) graph this equation. what is the meaning of its y-intercept, and the meaning of its slope?