Solution of problem N1431 Bernoulli probability theory

Solution of problem N1431 Bernoulli probability theory

1431. The probability that the lamp will burn after 1000 hours of operation is 0.8.
a) What is the probability that, after working 1000 hours, three out of five light bulbs will remain serviceable?
b) Find the probability that at least three of the five lamps remain functional (event A).

Additional information:

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