Assume for 2013 that Don made one transfer involving his grandson as follows: Don opened a joint checking account with his grandson, with right of survivorship, for his grandson's college expenses. Don made an initial deposit of $100,000. During 2013, grandfather wrote checks on the account to the university for grandson's tuition of $15,000 and grandson's living expenses of $20,000. What is the amount of the taxable gift for federal gift tax purposes?
a. 0.
b. $6,000.
c. $20,000.
d. $35,000.