Question $1$Fish caught by human beings can be turned into fish meal, and the fish meal can be used as feed to produce meat for human beings or used directly as food. The direct use of fish meal significantly increases the efficiency of the food chain.However, fish$-$protein concentrate, primarily for aesthetic reasons, is used as a supplementary protein food. As such, it competes with soy and other oilseed proteins. In the processing of the fish, after the oil is extracted, the fish cake is dried in rotary drum dryers, finely ground, and packed. The resulting product contains $65\%$ protein. In a given batch of fish cake that contains $80\%$ water $($the remainder is dry cake$),100$ kg of water is removed, and it is found that the fish cake