2. The protein of corn is 3.8%, so the protein of 20 kg of corn is 0.7 kg.

3. Rapeseed cake contains 32% protein, so the protein of 5 kg rapeseed cake is 2.4 kg.

4. The protein content of high-quality imported fishmeal is above 60%. Protein of domestic high-quality fishmeal is above 55%, so protein of 5 kg fishmeal is 2.75 kg protein.