Kevin co followup

Unless they are zero coupon bonds then you will use whatever the coupon rate is given in the question (after tax). If they are zero coupon bonds then obviously there is no interest - you can't invent interest when there is none!!

Sir then how we will calculate gross redemption yield on deep discounted bonds in that question?

You have not said which question you are asking about. You calculate exactly as normal - set up the flows (interest (if any) and repayment) and calculate the IRR. The approach is the same for all redeemable debt - it makes no difference if they are deep discounted. All it means is that there will be low interest (or zero interest if they are zero coupon bonds). You must have an answer to the question and it should be clear from the answer.