$$Wichita$\text{'}$s famous Sethi Restaurant is open $24$ hours a day. Servers report for duty at $3$ A$.$M$.,7$ A$.$M$.,11$ A$.$M$.,3$ P$.$M$.,7$ P$.$M$.,$ or $11$ P$.$M$.,$ and each works an$8-$hour shift. The following table shows the minimum number of workers needed during the $6$ periods into which the day is$$ divided: