For the purposes of this section "expenses reasonably incurred " means—
(a) in relation to a person who receives treatment at a hospital as an in-patient, an amount for each day he is maintained in the hospital representing the average daily cost, for each in-patient, of the maintenance of the hospital and the staff thereof and the maintenance and treatment of the in-patients therein; and
(b) in relation to a person who receives treatment at a hospital as an out-patient, reasonable expenses actually incurred.