Four forces of magnitudes 20 N, 40 N, 60 N and 80 are acting respectively along the four sides of a square ABCD as shown in figure. The magnitude of resultant is

A

$$40\sqrt{2}$$ N

B

$$50\sqrt{2}$$ N

C

$$45\sqrt{2}$$ N

D

$$60\sqrt{2}$$ N