In $1992$, average starting salaries offered to software students = $Rs. 5,290/month$
In $1996$, average starting salaries offered to software students = $Rs. 8,640/month$
∴ Total increase in $4$ years = $(8640-5290) = 3350$
∴ Percentage increase = $\dfrac{3350}{5290} = 63.32\%$
∴ Average per year increase = $\dfrac{63.32}{4}\% = 15.83\%$