A system includes a biological sensor measuring biological data of a plurality of customers, a storage storing a plurality of attendant-associated data records, and a processor. Each attendant-associated data record includes the biological data of a customer, a seat identifier, and an attendant identifier associated with each other. The processor calculates at least one stress indicator of at least one customer. Each stress indicator is calculated based on the biological data in one of at least one attendant-associated data record extracted from the plurality of attendant-associated data records and associated with a first attendant identifier. The processor further calculates an evaluation value indicated by the first attendant identifier based on the at least one stress indicator of the at least one customer. The evaluation value is updated based on a registered evaluation value identified by the first attendant identifier stored in the storage, and the calculated stress indicator.