Todd Radford has invented a new type of low-friction broom. After giving the matter much thought, Todd is pretty sure he will quit his $2,000 per month job with a janitorial service and produce and sell the brooms full time. Todd will rent a small building and use it as a production plant. The rent will be $1,500 per month. Todd will rent production equipment at a cost of $550 per month.

The cost of materials for each broom will be $11.50. Todd will hire workers to produce the brooms. They will be paid $4.25 for each completed unit. Todd will rent a room in the house next door for use as his sales office. The rent will be $250 per month. He has arranged for the telephone company to add voicemail to his home phone to get after-hours messages from customers. The addition of voicemail will increase his monthly phone bill by $5.

Todd has some money in savings that is earning interest of $1,100 per year. These savings will be withdrawn and used for about a year to get the business going. To sell his brooms, Todd will advertise heavily in the local area. Advertising costs will be $450 per month. In addition, Todd will pay a sales commission of $0.80 for each broom sold. For the time being, Todd does not intend to draw any salary from the new company. Todd has already paid the legal and filing fees to incorporate his business. These fees amounted to $1,500.

All of the costs listed above, except one, are differential costs between the alternatives of Todd producing brooms or staying with the janitorial service. Which cost is not differential?

	Todds present salary of $2,000 per month
	Rent on the production building, $1,500 per month
	Rent of production equipment, $550 per month
	Materials for producing brooms, at $11.50 each
	Labour cost of producing brooms, at $4.25 each
	Rent of room for a sales office, $250 per month
	Voice mail, $5 per month
	Interest lost on savings account, $1,100 per year
	Advertising cost, $450 per month
	Sales commission, at $0.80 per broom
	Legal and filing fees, $1,500