first, you add the tax to 72.50. 72.5 + 72.5 x 0.04 + 72.5 x 0.0725 and it will be 80.66, now the second part, so we take 20% of from 89.90. 89.9 - 89.9 * 0.2 and that will be 71.92 now we add 71.92 + 71.92 x 0.04 + 72.5 x 0.0725 and that is 80.01 so he should go with the dicounted price