strong data-start="73" data-end="88">Quantity I:  An article is marked 36% above its cost price and then sold at a discount of ₹168, resulting in a selling price of ₹x. When the same article is marked 28% above its cost price and sold after a discount of ₹144, the final selling price becomes ₹y. Given that the ratio of y to x is 18:19, determine the cost price of the article. Quantity II:  A sum of ₹12,600 is invested for 2 years at an annual compound interest rate of (x - 1)%, yielding ₹2,646 as interest. Find the compound interest earned on investing ₹5,600 for 2 years at an interest rate of (x + 4)%, compounded annually.