Calculate the ROR for the incremental net cash flow (X - Y), given the data below. Note that the appropriate increment is (X - Y), not (Y - X), because the initial cost of X exceeds the initial cost of Y.

Alternative	X	Y
Initial Cost ($k)	40	30
Uniform Annual Benefit ($k)	12	10
Life (years)	8	8
Salvage Value EOY 8	0	0
ROR (%)	24.95	28.98

Which of the selections below is correct?

a) ROR = 24.95% = ROR of X, because X is more costly

b) ROR = 36.721%, the interest rate that is the solution to: NPW = 0 = -30 + 12(P/A,i%,8)

c) ROR = 28.98% -24.95% = 4.03%

d) ROR = 11.81%, the interest rate that is the solution to: NPW = 0 = -10 + 2(P/A,i%,8)