To find the value of the given summation, we need to plug n=2,3,4,5,6 and find the value of the expression. And finally we need to add all of them .
When n=2, we will get 0.5 .
When n =3, we will get 1.
When n =4, we will get 3
When n =5, we will get 12
When n=6, we will get 60
Adding them, we will get 0.5+1+3+12+60 = 76.5
Therefore correct option is the last option .