A Cash Basis Calendar Year C Corporation in Athens,Georgia,has $100,000

A cash basis calendar year C corporation in Athens,Georgia,has $100,000 of accounts receivable on the date of its conversion to an S corporation on February 14.By the end of the year,$60,000 of these receivables are collected.Calculate any built-in gains tax,assuming that there is sufficient taxable income.

A) $0.
B) $21,000.
C) $28,000.
D) $35,000.
E) Some other amount.