There are three groups $$G_1, G_2$$ and $$G_3$$ in a College with 20, 40 and 60 students respectively. The average marks obtained by groups $$G_1, G_2$$ and $$G_3$$ are 50%, 60% and 70% respectively. Find the average marks of the entire college?

A

60%

B

63%

C

62%

D

61%