How is the prize money for the tennis games determined? Do the official sponsors put up all the money?

For example, the sponsors for the Australian Open were Kia, IBM and Garnier; did they all put up a piece or does the Australian have a "bank" that they draw from to pay out the prize money?How is the prize money for the tennis games determined? Do the official sponsors put up all the money?
bank and fans and all the money it earns from sponsers

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