In securing the shares for all accounts under her management, Linda Kammel of Northwest Futures purchased three blocks of shares at three different prices. She then allocated these shares by placing shares from the first block in accounts with surnames beginning with A-G. The second was allocated over accounts H-P, and the third over Q-Z. This action is:（）

A. not permissible under the Code and Standards.

B. consistent with her responsibilities under the Code and Standards.

C. permissible so long as the commissions per share are the same across all accounts.

出售某种文具盒，若每个获利x元，一天可售出（6-x）个，则当x=______元时，一天出售该种文具盒的总利润y最大．