If Tax Returns slips are not available with you, and you are a private sector salaried employee then you can ask your employer company for Form 16 and they can help you in this or you should be maintaining your ITR file. So ask your CA to get you those files. And if your per month pay is Rs. 28250, then EMI cannot be exceeded above Rs. 15000 as it is adjusted keeping in mind the living cost of an individual. To get the exact quote on EMI for 5 years, kindly visit the below link: -
New Tata Nano with EasyShift is available at Rs. 2 lac (Ex-showroom, Delhi), and the final cost depends on the valuation of your car. So, first get the valuation of your car from authorized Tata dealer, so he can give you a final quote for the new car.