6-4. Three mutually exclusive design alternatives are being considered. The estimated sales and cost data for Investment cost $30,000 $60,000 $50,000 Estimated units 15,000 20,000 18,000 to be sold/year Unit selling price,3.50 $4.40 $4.10 Variable costs, $1.00 $1.40 $1.15 Annual expenses $15,000 $30,000 $26,000 (fixed) Market value Useful life 0 $20,000 $15,000 10 years 10 years 10