Answer:
a) before income taxes are considered
we need to calculate the present value of the associated cash flows:
PV alternative A = -$10,000 / 1.15 - $10,000 / 1.15² - $10,000 / 1.15³ - $10,000 / 1.15⁴ + $90,000 / 1.15⁵ = -$8,695.65 - $7,561.44 - $6,575.16 - $5,717.53 + $44,745.91 = $16,196.13
PV alternative B = $50,000 / 1.15⁵ = $24,858.84
Alternative B is better because its PV is higher.
b) after income taxes are considered when t=40%
PV alternative A = -$6,000 / 1.15 - $6,000 / 1.15² - $6,000 / 1.15³ - $6,000 / 1.15⁴ + $54,000 / 1.15⁵ = -$5,217.39 - $4,536.86 - $3,945.10 - $3,430.52 + $26,847.54 = $9,717.67
PV alternative B = $30,000 / 1.15⁵ = $14,915.30
Alternative B is better because its PV is higher.
c) is there a different selection before and after income taxes are considered?
no, both times alternative B was the best alternative