() \({\hat{V}}_{12}=\frac{2k}{x_{2}-x_{1}}\ln\left(\frac{{\hat{\delta}}_{2}}{{\hat{\delta}}_{1}}\right)=\frac{2k}{x_{2}-x_{1}}\ln\left(\frac{\delta_{2}+\varepsilon_{2}}{\delta_{1}+\varepsilon_{1}}\right)\text{\ \ .}\)