Let x be the cost and the pre-tax receipt is between $11.57 and $81.43, so
11.57≤ x ≤ 81.43
Let y be the difference in taxes then,
11.57*(9.75/100 - 7.75/100) ≤ y ≤ 81.43*(9.75/100 - 7.75/100)
=11.57*(0.0975 - 0.0775) ≤ y ≤ 81.43*(0.0975 - 0.0775)
= 11.57*0.020 ≤ y ≤ 81.43*0.020
= 0.2314 ≤ y ≤1.6286
To the nearest cent, it is
0.23≤ y ≤1.62
Please find attached the graph.