دشواری: 70%

Investigating in how many ways objects of two different colours can be grouped

Having three black objects B and one white object W they can be grouped in 7 ways like this:

(BBBW)(B,BBW)(B,B,BW)(B,B,B,W) (B,BB,W)(BBB,W)(BB,BW)

In how many ways can sixty black objects B and forty white objects W be thus grouped?

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