985. The textbook is published in a circulation of 20,000 copies. The probability that the textbook is stitched incorrectly is 0.0002. Find the probability that the circulation contains
a) exactly 4 defective textbooks;
b) less than 4 defective textbooks;
c) more than 4 defective textbooks;
d) at least one defective textbook.

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