4689. For each lottery ticket with probability p1=0.15, a big win can fall, with probability p2=0.15, a small win, and with probability p3=0.7, the ticket can end up without a win. Bought n=15 tickets. Determine the probability of getting n1=2 big wins and n2=1 small ones.

Detailed solution. Decorated in Microsoft Word 2003 (Quest decided to use the formula editor)