tax deducted at source

I have a problem regarding levy of TDS in the following matter:

M/s. X Partnership firm, an Importer of Iron & Steel, has imported Zincc lot from abroad.

The Supplier of goods has made an arrangement with m/s X and issued a Bill as follows:

BILL

ZINC                                                                                         $ 10,00,000 

Add: Interest (As Buyer's Credit for 90 Days)                   $       20,000

                                                         T    O    T    A    L             $ 10,20,000

1.     Whether the above Interest is liable to Tax Deduction at source?

2.     If Yes at what percentage?

3.     Whether the above interest is considered as part of Purchase cost?

        Please Answer the above Query as soon as possible.........