I am doing a feasibility study for the startup of a block production factory with automatic production line so I want to ask some few questions please:

1) How many bags of cement will use up a 20ton trip of sharp sand for commercial block production (9", 6", 5", 4" or better phrased: How may tons of sand will be required to mould 35-40 blocks from 1 bag of cement?

2) What is the optimal mixture of cement, sharp sand, soft sand and stone dust for good commercial block production?

3) How much water is optimal per bag of cement?

4) Do I really need to include soft sand in the mixture? If yes then why?

Your responses will be highly appreciated. Pardon me for not using the right civil engineering terms.