The analyst in the Dorben Company wishes to assign a number of like facilities to an operator

Question:

The analyst in the Dorben Company wishes to assign a number of like facilities to an operator based on minimizing the cost per unit of output. A detailed study of the facilities revealed the following:
Loading machine standard time = 0.34 minutes
Unloading machine standard time = 0.26 minutes
Walk time between two machines = 0.06 minutes
Operator rate = $12.00 per hour
Machine rate (both idle and working) = $18.00 per hour
Power feed time = 1.48 minutes
How many of these machines should be assigned to each operator?