How to find product with maximum discount SQL HackerRank

I'm having trouble with a SQL problem in HackerRank (so no rank or window functions) and would appreciate any tips. Noob so please be gentle.

Product_Id Product_Name Category Price Discount Available
1 P-1 C-5 720 10 1
2 P-2 C-1 935 17 1
3 P-3 C-2 588 19 1
4 P-4 C-4 619 5 0
5 P-5 C-1 803 16 1


I want to know which product is on maximum discount for each category. In the case of multiple products having same maximum discount within a category, print the product with the minimum product_id.

Sample Output

C-1 2 17
C-2 3 19
C-4 4 5
C-5 1 10


http://sqlfiddle.com/#!18/1a492d ^I've put here what I've tried so far. I'm not sure how to get the product for the maximum discount. I also don't know how to handle if there's multiple products with the same maximum discount?

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