Ratan's expenditure and savings are in the ratio $5:1$. If his salary is increased by $25\%$ and savings by $15\%$, the percentage increase in his expenditure is:

If the simple interest on a certain sum of money for three years in $Rs. 225$ and the compound interest on the same sum at the same rate for $2$ years is $Rs. 150$, then the principal invested, in rupees, is ________.