1.21. There are 100 products (including 4 defective) in a batch. The batch is arbitrarily divided into two equal parts which are sent to two consumers. In how many ways all defective products will be got: a) by one consumer; b) by both consumers fifty-fifty?

1.22. A library consists of ten different books, and five books cost on 4 thousands of tenghe each, three books - on one thousand of tenghe and two books - on 3 thousands of tenghe. In how many ways two randomly taken books cost 5 thousands of tenghe.