How many words of memory map to the same cache entry?

I am going over some practice questions for the Major field exam and it asks:

A processor with a word-addressable memory has a two-way set-associative cache. A cache line is one word, so a cache entry contains a set of two words. If there are M words of memory and C cache entries, how many words of memory map to the same cache entry?

I am not sure how to even approach this problem since I am not too familiar with computer organization. Any help would be appreciated. Thanks!

• If you aren't familiar with cache organisation, then you should go over it once before attempting it. This is a fairly easy problem. This should cover most of what you need. – Gokul Dec 2 '18 at 7:57
• Since when gre started taking computer science subject test! :O – Mr. Sigma. Dec 2 '18 at 11:22

Cache has C/2 fixed locations
M / (C/2) = 2M/C