There are nine machine in the automatic lathe section of a certain machnine shop.The set up time on the an automatic late average $6$hours.The average operation of the time $8$ minute under shop rules an operation can be assigned to run up to the three operators in the section of nine lathes in addition to the lathe operators there are two set up workers who perform machine setup eclusively.These set up workers are kept busy full shift.the section run one $8$ hours per day $,6$ days per week $.$however an average of $15\%$ of the production time is lost due to the machine breakdown $.$Scrap loses are negligible $.$The production controlmanager claims that pcapacity of the section should be $1836$ pieces per week however the actual output average only $1440$ units per week.what is the problem