Moon Tower is a small fast$-$food outlet located in Houston and serving mainly the corporate clientele. Moon Tower$’$s main fare is a freshly prepared, customizable line of sandwiches. It is supplemented with an assortment of drinks, light salads, seasonal fruit, and snacks. The restaurant is open from $10$:$00$AM to $10$:$00$PM$,$ but the peak demand is during lunch hours, $11$:$30$AM to $2$:$00$PM$.$  A customer joining the line makes a sandwich selection by consulting the billboard, marks the selection on a customized form, and hands the form to one of several assemblers who make the sandwich. The customer does not wait for the sandwich to be assembled but proceeds directly down the line to select additional items onto their tray. Next, the customer proceeds to pay at the cash register. Finally, after the payment is completed, they collect the prepared sandwich at the pick$-$up location. Selecting the sandwich and marking the form takes $45$ seconds. Assembling the sandwich requires $90$ seconds. Selecting additional items takes $60$ seconds. Paying at the cash register requires $40$ seconds. Collecting the prepared sandwich requires $20$ seconds. The restaurant employs $2$ cash registers and $6$ sandwich assemblers, and one person to disburse the prepared sandwiches.

what is the theoretical flow time of the process?