*must be done in excel spreadsheets*

Electricity costs are evaluated as follows:

If 500 or fewer units are used, cost is $0.02 per unit. If 501 1000 units are used, cost is $0.02 for first 500, $0.04 for remaining. If more than 1000 are used, the cost is $0.02 for first 500, $0.04 for next 500, and $.08 for remaining.

a) Create a spreadsheet where a user can enter the number of electricity units used, and display the total cost.

b) Make a plot of cost versus units.