In $\triangle ABC, AB = 20$ cm, BC = 21 cm and AC = 29 cm. What is the value of $\cot C + cosec C - 2 \tan A$?

$\frac{3}{5}$ $\frac{9}{20}$ $\frac{2}{5}$ $\frac{7}{20}$

$\frac{2}{5}$