John enjoys boxing and engages a personal trainer to improve his health and fitness. As part of a special offer, John pays $0 for the first session and $30 for each subsequent session. John gains $200 of benefit from attending 6 sessions and $250 of benefit from attending 7 sessions.

Which of the following statement(s) are true:

A.John should attend the seventh session because the marginal benefit is greater than the marginal cost.

B.The marginal benefit of attending the seventh session is $40.

C.John should not attend the seventh session because the marginal benefit is less than the marginal cost.

D.The marginal cost of attending the seventh session is $50.