A river barge, whose cross section is approximately rectangular, carries a load of grain. The barge is \(28 \mathrm{ft}\) wide and \(90 \mathrm{ft}\) long. When unloaded, its draft (depth of submergence) is \(5 \mathrm{ft}\). and with the load of grain the draft is \(7 \mathrm{ft}\). Determine:

(a) the unloaded weight of the barge, 

(b) the weight of the grain.