3. Tilly Company had the following cost and volume data for the first four months of the year. January: Cost of $52,500; volume of 9,000 units February: Cost of $40,000; volume of 6,500 units March: Cost of $70,000; volume of 14,000 units . April: Cost of $60,000; volume of 11,000 units Using the tast-squares methodor the scattergraph method, which one of the following is the best estimate of the variable cost per unit? $4.00 per unit $8.00 per unit $10.00 per unit $15.00 per unit $25.00 per unit $35.00 per unit