Answer:
Part 4
4 | a. When Peter wrote: I = 275(.8)(12), he wrote the rate of 8% as 0.80 instead of 0.08.
4 | b. The correct interest is $264.
Part 5
5 | a. Isabella multiplied 3000*0.04*6 incorrectly, she probably forgot that she multiplied 3000 into the expression.
5 | b. The correct interest is $720.