42.
John and Mary own shares of stock in a certain company. Does John own more shares of the company's stock than Mary?
(1) Mary owns more than 500 shares of the company's stock.
(2) The number of shares of the company's stock that John owns is 400 less than twice the number of shares of the company's stock that Mary owns.
題目問john的股份有沒有比Mary多
1.mary多有500個股份
2.john有的股份比mary有股份兩倍再少400
兩個看起來都sufficient
但為何答案是C?