Willow brook National Bank operates a drive-up teller window that allows customers

Willow brook National Bank operates a drive-up teller window that allows customers to complete bank transactions without getting out of their cars. On weekly mornings, arrival to the drive-up teller window occur at random, with an arrival rate of 24 customers per hour or 0.4 customers per minute.
A. what is the mean or expected number of customers that will arrive in a five-minute period?