Solve the following equation.
$$\left(7^{3} - 7^{2} + 6 \right) \times \left(6^{3} - 2^{3} - 3^{2} + 1 \right) \div \left(21^{2} + 20^{2} - 41 \right) $$= ___________.

A

75

B

40

C

50

D

25