Solution of problem N4195 Laplace probability theory

Solution of problem N4195 Laplace probability theory

4195. In the Sberbank branch of a microdistrict, an ATM is used by 20% of the population from nearby houses. What is the probability that out of 500 at random the selected residents of the microdistrict in this branch of Sberbank use an ATM:
a) 90 people;
b) from 80 to 130 people;
c) more than 120 people?

Additional information:

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