To find the percentage by which Henry's total amount paid is less than Anne's total amount paid, we need to compare the difference in the total amounts to Anne's total amount and express it as a percentage.
Anne's total amount paid, including sales tax, is $2,000 + 5% of $2,000.
Anne's total amount paid = $2,000 + 0.05 * $2,000 = $2,000 + $100 = $2,100.
Henry's total amount paid, including sales tax, is $1,800 + 12% of $1,800.
Henry's total amount paid = $1,800 + 0.12 * $1,800 = $1,800 + $216 = $2,016.
The difference between Anne's and Henry's total amounts paid is $2,100 - $2,016 = $84.
To find the percentage difference, we calculate (Difference / Anne's total amount paid) * 100:
($84 / $2,100) * 100 = 4%.
Therefore, Henry's total amount paid, including sales tax, is 4% less than Anne's total amount paid, including sales tax. This corresponds to option (B).