Three alternatives are being considered. Alternative A has a useful life of 6 years; WILEY \(\oplus\) Alternative B, 2 years; and Alternative C, 3 years. What is the difference (in years) between the planning horizons determined by the longest life approach and the least-common-multiple approach?

a. 0 years

b. 6 years

c. 12 years

d. 30 years