Harold (age 63) established a trust and named his wife, Betty (age 40) as income beneficiary for 20 years. After 20 years, Harold's son, Nelson (age 30) and nephew, Ben (age 22) are to receive lifetime income interests. After the death of both Nelson and Ben, the remainder passes equally to Harold's granddaughter Amy (age 20) and great-grandson, Mason (age 1). Assume Nelson died 22 years after the trust was established, and Ben died 34 years after the trust was established. Assuming both Amy and Mason were alive when Ben died, how many times is the generation-skipping transfer tax levied?

a. Never.

b. Once.

c. Twice.

d. Three times.