Answer:
This test batch can be chosen in 2380 ways
Step-by-step explanation:
The order in which the batteries are chosen is not important. So we use the combinations formula to solve this question.
Combinations formula:
is the number of different combinations of x objects from a set of n elements, given by the following formula.

In how many ways can this test batch be chosen?
4 batteries from a set of 17. So

This test batch can be chosen in 2380 ways
He mails
(1000) x (the number of weeks he keeps it up)
of them.