Answer
a. $P=300+0.05(s)$
b. 500 dollars
c. 9000 dollars
Work Step by Step
a. $P=300+0.05(s)$
b. $s=4000$
$P=300+0.05(4000)$
$P=300+200$
$P=500$
c. $P=750$
$750=300+0.05(s)$
$750-300=0.05(s)
$450=0.05(s)
$450\div0.05=s$
$s=9000$