Make money. Twenty quail eggs cost 5 yuan to make money, and 5 yuan can buy half a catty of quail eggs. Quail eggs in the market cost ten yuan a catty, and five yuan can only pay half a catty. A quail egg weighs about10g, and half a catty is 250g, resulting in 25 quail eggs. Although small, it has a high nutritional value, almost three times that of eggs. It can be said to be the best tonic for mental workers.