Formula for finilazing resale value of product and to know the profit after Tax dues

Hello,

Can someone please help me with the below detailed issue; I need a formula for this calculation.

I am a re-seller and I purchase from the Distributor. The MRP (Maximum Retail Price)  is  printed on the boxes and the MRP is inclusive of 18% tax. Suppose the MRP is Rs. 10000

The Distributor sells it to the re-seller at Dealers Price and not at MRP and the re-seller further sells it to his customer at MRP rate.

I pay tax to the Government by claiming input credit, that is, the tax paid to the distributor when I bought the product from him for onward sell.

Example:

MRP printed on the on the product is – Rs. 1000

Dealer sells it to me for - Rs. 800

I sell it to my customer with 10% discount on MRP, that is, for Rs. 900

The unseen breakup of rates:

a) Product cost Rs. 847.457 + Tax @ 18% Rs = 152.542 (Roundup Rs. 1000)

b) Dealer Price Rs. 677.966 + Tax @18% Rs = 122.033 (Roundup Rs. 800)

c) Sold at Rs. Rs. 762.711 + Tax @ 185 = 137.288 ( (roundup Rs. 900)

Tax due to the Government from me:

                                 Tax Charged to customer by re seller Rs. 137.288

                                 Tax already paid through the distributor Rs. 122.033

                                 Tax Due to pay    137-122= Rs. 15

How we arrive at profit :

Collected from resale =                                        Rs. 900

Paid to Distributor  =                                           Rs. 800

Balance Tax Due to Government                          Rs.  15

Total Cost to me =                                     (Rs. 800+Rs. 15)

Profit in the above sell is : (9.44%) Rs.85  (Rs.900-Rs. 800-Rs.15=Rs 85)

In view of above, I am seeking help to do a formula, which may be like this;

I should be able to choose option to give discount on MRP and then I should know how much profit I will earn on the product. or any other format to know my profit while fixing a price for resale.