Interior, Boundary, and Closure of Sets

I don't know how to solve these.

Heres the problem:

Find the interior, boundary, and closure of each set gien below. Then determine whether the given set is open, closed, both, or neither. Find the set of accumulation points, if any, of the set.

A. {1/n : n in the set of N}

B. N

C. [0,3] union (3,5)

D. {x in the set of R^3 : 0 less than or equal to 2 norm of x less than 9}

E. intersection from n=1 to infinity of (-1/n , 1/n)

F. union from n=1 to infinity of (-1/n , 1/n)

G. N^3, which is defined to be {(x,y,z) : x,y,z in the set of N}