An activated sludge process is being sized for a settled wastewater flow of $7\mathrm{.}40$ MGD containing$7900$ lb of BOD $($per day$).$ The design maximum BOD loading is $40$ lb$/1000$ ft $/$day$,$ and the design minimum aeration period is $6\mathrm{.}0$ hr$.$ Calculation the dimensions for $4$ identical aeration tanks. If the operating MLSS is $2000$ mg$/$L$,$ what is the calculated F$/$M at design loading?