A river barge, whose cross section is approximately rectangular, carries a load of grain. The barge is

$25$ ft wide and $93$ ft long. When unloaded its draft $($depth of submergence$)$ is $5$ ft$,$ and with the load of

grain the draft is $8$ ft$.$ Determine: $($a$)$ the unloaded weight of the barge, and $($b$)$ the weight of the grain.