Let the investments be:
Let the corresponding annual interest rates be:
Given: Bina's interest exceeds Amala's by ₹250
\[ \frac{20xy}{100} - \frac{18xy}{100} = 250 \Rightarrow \frac{2xy}{100} = 250 \Rightarrow 2xy = 25000 \Rightarrow xy = 12500 \]
Total interest = \[ \frac{18xy + 20xy + 20xy}{100} = \frac{58xy}{100} \] Substitute \( xy = 12500 \): \[ \frac{58 \cdot 12500}{100} = 7250 \]
\[ \boxed{₹7250} \]