If only one person from a group responds to a greeting of peace, is the reward for the entire group or only for the one who responded?

It was stated in Fatwa No. 41449 that returning the salutation to a group is a communal obligation (fard kifayah); if one of them returns it, the sin is lifted from the rest, but if no one returns it, all of them incur sin. It appears that the one who initiates the return of the salutation will earn reward.