1715. The worker serves 12 machines of the same type. The probability that the machine will require the worker's attention for an hour is 1/3. Find: a) the probability that within 4 hours of the machine will require the attention of the worker; b) the most probable number of machines that will require the attention of the worker for an hour.

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