The answer to a and c are 80 units, but I cannot figure out how to get b and d

Modern Artifacts can produce keepsakes that will be sold for $60 each. Nondepreciation fixed costs are $1,400 per year, and variable costs are $30 per unit. The initial investment of $5,000 will be depreciated straight-line over its useful life of 5 years to a final value of zero, and the discount rate is 12%.

a. What is the accounting break-even level of sales if the firm pays no taxes? (Do not round intermediate calculations. Round your answer to the nearest whole number.) Acounting break-even level of sales units 80

b. What is the NPV break-even level of sales if the firm pays no taxes? (Do not round intermediate calculations. Round your answer to the nearest whole number.) NPV break-even level of sales units

c. What is the accounting break-even level of sales if the firms tax rate is 20%? (Do not round intermediate calculations. Round your answer to the nearest whole number.) Acounting break-even level of sales units 80

d. What is the NPV break-even level of sales if the firms tax rate is 20%? (Do not round intermediate calculations. Round your answer to the nearest whole number.) NPV break-even level of sales units