The initial cost of each jar of grape jam is calculated by dividing the cost of one case by the number of jar in each case. That is,
cost per jar = $7.20 / 12
cost per jar = $0.6
The mark-up is calculated by dividing the difference of the new cost and the previous cost by the previous cost.
mark up = (($0.89 - $0.6) / $0.6) x 100% = 32.58%.
