Pls help

Your cupcake bakery has 10 professional ovens, the oldest of which you're considering replacing.
	This oven was purchased 7 years ago for $10,000. You are depreciating it over a 10-year life toward
	a zero salvage value, using straight-line depreciation (the method you use for all of your ovens).
	This oven costs $2,000/year to operate, and you believe it would continue to run for 5 more years.
	You could sell it today for $750.
	The replacement you're considering costs $22,500. You expect that this oven will have a useful life
	of 5 years (which is also its depreciable life). It would be cheaper to operate than the current oven,
	costing only $1,000/year to run. While you would depreciate it toward a zero salvage value (your standard
	practice), you believe it would actually have a market value of $600 after 5 years.
	Your marginal tax rate is 35% and your required return (your WACC) is 20%.
	Use NPV to decide whether or not you should purchase the new oven.
	Notes:
	*We will assume, as your book does, that any tax effect from the sale of the old machine happens at t=1
	(today is t=0, so t=1 is in one period). Likewise, any tax effect from the sale of the "new" machine will
	occur one year after its sale.