The formula to estimate the convexity of a bond given price changes is:

$\text{Convexity} = \frac{V_+ + V_- - 2 \times V_0}{V_0 \times (\Delta y)^2}$

Given the data:

• $V_0$ (price at 2.15%) = 99.100
• $V_-$ (price at 2.13%) = 100.115
• $V_+$ (price at 2.17%) = 98.250
• $\Delta y$ (change in yield) = 2.15% - 2.13% = 0.02% = 0.0002

Step-by-step calculation:

1. Numerator: $V_+ + V_- - 2(V_0) = 98.250 + 100.115 - 2(99.100) = 198.365 - 198.200 = 0.165`$2. **Denominator:** $V_0 \times (\Delta y)^2 = 99.100 \times (0.0002)^2 = 99.100 \times 0.00000004 = 0.000003964$3`. **Convexity:** `$0.16`5 / 0.000003964 \approx 41,624.62$

Thus, the estimated convexity of the bond is 41,624.62.