Mains Size Calculation for 800A Supply

I'm seeking an experienced electrical engineer to calculate the size of the consumer's mains required for an 800A supply for an industrial building. The mains run from the supply to the main switchboard is less than 50 meters, and future load expansion does not need to be considered... (Budget: $250 - $750 AUD, Jobs: Circuit Design, Electrical Engineering, Electronics, Engineering, Industrial Engineering, Mechanical Engineering)