Alia purchased two items: a bag X, and another bag Y. She later sold them for a profit. The disparity in the sale prices of X and Y is Rs. 200. The cost she paid for X is represented as (a + b), while the amount she spent for Y is expressed as (b + 400). It's also mentioned that 'b/a' equals 2, and both a and b are integers. The obtained profit percentages after selling X and Y are 25% and 60% respectively. Calculate the original cost of the bag X?