What is the difference between the biggest and the smallest fraction among the following fractions?
$$\frac{4}{5},\frac{5}{6},\frac{3}{8},\frac{5}{7},\frac{6}{7}$$

A

$$\frac{13}{49}$$

B

$$\frac{15}{28}$$

C

$$\frac{27}{56}$$

D

$$\frac{15}{42}$$