Customer Free of charge supply - scheme to be mentioned in Shipping bill - Reg - Customs - Exim - SEZ

Hi All, Need support in below scenario : A customer wants to provide material free of charge (Say Rs.20/- worth material) to build a equipment, we are planning to import the same by paying import duty (We don't want to have obligation of sending the Finished equipment within specific time, so dint opt for jobbing or equivalent scheme - so planning to pay the duty). We will procure material (Say Rs.80/-) and add our overhead and profit (Say Rs.20/-) and export the shipment. Customer will issue PO for Rs.100/- and we will make invoice for Rs.100. We want to avail drawback and RODTEP benefits. We want to know the following 1) What should be the export invoice price. Option #1 : Invoice value : Rs.100/- and net payable Rs.100 (or) Option #2 Invoice value Rs.120 free of charge item : Rs.20/- , Net payable Rs. 100/- 2) How we should make Shipping bill : Option #1 : SB rate : Rs.100/- FOB price : Rs. 100/- , and mention the free of charge material imported BOE details in remarks. Option #2 : SB rate : Rs. 120/- and deduction : Rs.20/- and FOB price will be Rs.100/- ,and mention the free of charge material imported BOE details in remarks. 3) We want to capture in government records that free of charge materials has been reexported. is the above method correct (or) do we have any other method. Thanks for your feedback in advance.