Her commission rate is 7.44%
The parameters given are;
The amount Mary earns annually = $28,000
The amount Mary grossed during a week = $658.0.
The amount Mary had sold during the week to make the amount grossed during the week = $1673.19
Given that Mary makes $28,000 per year
Therefore;
The amount Mary earns per week = Amount earned per year/52
The amount Mary earns per week = $28,000/52 = $538.46
The amount extra she made on commission = $658.00- $538.46= $119.54
The commission rate = Commission earned/(Amount of merchandise sold)×100
The commission rate = 119.54/1673.19 × 100 = 7.14%
Her commission rate = 7.44%