C = $\frac{10}{7.12}$ + $\frac{10}{12.17}$ + $\frac{10}{17.22}$ +...+ $\frac{10}{502.507}$
C = 2 . ($\frac{5}{7.12}$ + $\frac{5}{12.17}$ + $\frac{5}{17.22}$ +...+ $\frac{5}{502.507}$)
C = 2 .($\frac{1}{7}$ - $\frac{1}{12}$ + $\frac{1}{12}$ - $\frac{1}{17}$ + $\frac{1}{17}$ - $\frac{1}{22}$ +...+ $\frac{1}{502}$ - $\frac{1}{507}$)
C = 2 . ($\frac{507}{3549}$ - $\frac{7}{3549}$)
C = 2 . $\frac{500}{3549}$
C = $\frac{1000}{3549}$
