MODEL:
! Arrival rate of customers/ hour;
   AR = 25;
! Service time per customer in minutes;
   STM = 6;
! Service time per customer in hours;
   STH = STM/ 60;
! Fraction customers finding all servers busy;
   FB = .05;
! The PEL function finds number of servers needed, NS;
   FB = @PEL( AR * STH, NS);
END