With some trial and error you can find that if you sell the table for Rs. 7 and Rs. 14 (notice that one price is twice the other, as given in the question), you will incur losses of 93%(L1) and 86%(L2) respectively. Here L1 - L2 = 7, which satisfies the given condition.
Now you can use the unitary method -
Rs. 7 corresponds to Rs. 210 Rs. 1 correspond to Rs. 30 Rs. 100 correspond to Rs. 3000 (which is the CP of the Table)