Please solve it

Hi, I realised there is a small error in the above model, use Wdv depreciation for tax savings as SLM method is not allowed. 

The Indian companies act allows SLM depreciation but not the Tax act. Since, there is no depreciation rate mentioned here, you can follow SLM method with full tax paid without arrears. This question is not so well structured. Coming to the sensitivity analysis, You have to find out what amount of changes in the variables like no. of units, selling price or Variable costs will make NPV=0 (Break even). This is the best method of simulation in financial modelling. Other wise, there are formulas to find out what independent variable should increase or decrease to make NPV=0, but I am unaware of the logical formulas for your question requirements. The sensitivity analysis has drawbacks like changes to amounts required are individual i.e., you have change every single variable to check at what amount will NPV=0.  Time consuming!