• (A) 条件(1)充分，但条件(2)不充分．
• (B) 条件(2)充分，但条件(1)不充分．
• (C) 条件(1)和(2)单独都不充分，但条件(1)和条件(2)联合起来充分．
• (D) 条件(1)充分，条件(2)也充分．
• (E) 条件(1)和条件(2)单独都不充分，条件(1)和条件(2)联合起来也不充分．

Joan had a total of $16.50 in her coin bank. How many quarters does she have
(1) The bank contains only quarters and dimes.
(2) There were 81 coins in the bank.