Solution of problem N1293 Poisson probability theory

Solution of problem N1293 Poisson probability theory

1293. The telephone exchange serves 1,000 subscribers, the probability that a subscriber needs a connection within a minute is 0.0007. Find the probability that at least three calls will be made to the telephone exchange per minute.

Additional information:

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