D = $\frac{5}{1.4}$ + $\frac{5}{4.7}$ + $\frac{5}{7.10}$ + ... + $\frac{5}{91.94}$
= $\frac{5}{3}$ . ($\frac{3}{1.4}$ + $\frac{3}{4.7}$ + $\frac{3}{7.10}$ + ... + $\frac{3}{91.94}$)
= $\frac{5}{3}$ . (1 - $\frac{1}{4}$ + $\frac{1}{4}$ - $\frac{1}{7}$ + $\frac{1}{7}$ - $\frac{1}{10}$ + ... + $\frac{1}{91}$ - $\frac{1}{94}$)
= $\frac{5}{3}$ . (1 - $\frac{1}{94}$)
= $\frac{5}{3}$ . $\frac{93}{94}$
= $\frac{155}{94}$
= 1$\frac{61}{94}$
