Solution of problem N1351 Laplace probability theory

Solution of problem N1351 Laplace probability theory

1351. In a box of 10 revolvers of one system and identical in appearance, 4 of them not shot. The probability of hitting a target from a non-shot revolver is 0.3, and from the targeted revolver it is 0.9. Out of the randomly taken revolver, 200 shots were fired at the target. What is the probability that the number of hits on the target is between 120 and 150?

Additional information:

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