Customs for two new laptops bought in USA

I was going to take two laptops from USA to India, as I am a computer science student. I generally use both of them for programming. As the law is stated in India, only one laptop is allowed as free allowance, and the other is dutiable good. Logically I am a tourist, as I will be returning to USA in twenty days, as my semester starts soon. So I should not be dutiable.

If the customs officer forces me to pay duties, then how much would it be?

First, both the laptops are $710 each. How is their worth calculated by customs officers (i.e. is the exchange rate considered on the buying day or on the day of travel)?

Second, since one of the laptops is free, does that mean I will be only charged duty for the other laptop?

Finally, I believe there's a minimum allowance while traveling (Rs 35000), so will I have to pay duty on $710 minus Rs 35000 or the entire price? Since that will be like only $710 = Rs 41655 minus Rs 35000 = Rs 6655 (*duty rate), that would not be more than 2K. (Does that mean I could buy a new laptop for my Mom and gift it to her while legally paying the duty? (Since 2k is flimsy.)) (I have no idea what the duty rate is!)