Investigation 1.1. Sales on Commission.
Delbert is offered a parttime job selling restaurant equipment. He will be paid $1000 per month plus a 6% commission on his sales. The sales manager tells Delbert he can expect to sell about $8000 worth of equipment per month. To help him decide whether to accept the job, Delbert does a few calculations.
 Based on the sales manager’s estimate, what monthly income can Delbert expect from this job? What annual salary would that provide?

What would Delbert’s monthly salary be if he sold only $5000 of equipment per month? What would his salary be if he sold $10,000 worth per month? Compute monthly incomes for each sales total shown in the table.
Sales Income 5000 8000 10,000 12,000 15,000 18,000 20,000 25,000 30,000 35,000  Plot your data points on a graph, using sales, \(S\text{,}\) on the horizontal axis and income, \(I\text{,}\) on the vertical axis, as shown in the figure. Connect the data points to show Delbert’s monthly income for all possible monthly sales totals.
 Add two new data points to the table by reading values from your graph.

Write an algebraic expression for Delbert’s monthly income, \(I\text{,}\) in terms of his monthly sales, \(S\text{.}\) Use the description in the problem to help you:He will be paid: $1000 . . . plus a 6% commission on his sales.Income \(= \fillinmath{XXXXXXXXXXXXXXX}\)
 Test your formula from part (5) to see if it gives the same results as those you recorded in the table.
 Use your formula to find out what monthly sales total Delbert would need in order to have a monthly income of $2500.
 Each increase of $1000 in monthly sales increases Delbert’s monthly income by .
 Summarize the results of your work: In your own words, describe the relationship between Delbert’s monthly sales and his monthly income. Include in your discussion a description of your graph.