To find the total amount Bentley paid, including tax, we first need to calculate the total cost of the folders and markers before tax, and then apply the sales tax.
- The cost for the folders is \(0.90f\), where \(f\) is the number of folders.
- The cost for the markers is \(0.40m\), where \(m\) is the number of markers.
The total cost before tax is: \[ 0.90f + 0.40m \]
Next, we need to account for the sales tax, which is 6%. To include the tax, we multiply the total cost by \(1.06\): \[ \text{Total cost including tax} = 1.06(0.90f + 0.40m) \]
Looking at the provided multiple choice answers, we can see that the correct expression that matches our calculation is: \[ 1.06(0.9f + 0.4m) \]
So, the correct answer is: 1, point, 0, 6, left parenthesis, 0, point, 9, f, plus, 0, point, 4, m, right parenthesis.