The velocity at which 6 kg mass (shown in figure) strikes the ground when it is released from a height of 6 m above the ground is __________ m/s. Assume pulley is massless and string is light and inextensible. (Take $$g = 10$$ m/s$$^2$$)

A

7.74

B

7.20

C

6.55

D

4.50