Solution of problem N4625 Poisson probability theory

Solution of problem N4625 Poisson probability theory

4625. Radio equipment consists of 1000 electrical elements. The probability of failure of one of them during the year of operation is 0.001 and does not depend on the state of other elements. What is the probability of failure:
a) two elements;
b) at least two and no more than four elements;
c) at least two elements per year?

Additional information:

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