Решение задачи N1923 теория вероятностей

1923. The publishing house´s expedition sent newspapers to two post offices. The probability of timely delivery to each of the post offices is 0.9. Find the probability that: a) both post offices will receive newspapers on time; b) only one postal distance will receive newspapers on time; c) at least one post office will receive newspapers on time.

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