Solution of problem N1444 Bernoulli probability theory

Solution of problem N1444 Bernoulli probability theory

1444. In the lighting of the premises of the company, 14 bulbs are used. For each bulb the probability that it will remain intact for a year is 7/8. What is the probability that during a year you will have to replace at least half of all the bulbs?

Additional information:

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