Answer: $90
Step-by-step explanation: use the form of y=mx+b to form your overall equation. since you're trying to find the final amount of money, y will be that final amount. since your starting number/cost is $50 you will replace b with 50. so now you have y=mx+50. if every CD costs $10 then your m will be 10, so now you are left with y=10x+50. if you're buying 4 CDs and m is your growth rate, then m will equal four, making your final equation y=10(4)+50. if you follow PEMDAS, then you will get y=40+50. y=90 so jenifer's final cost will be $90 for the CD player and the 4 CDs.