Math Question

Use the following formula for the sum of the cubes of the first integers to evaluate the limit in part (a). 1**3+2**3+...+n**3=((n(n+1))/2)**2 (a)lim n approaches infinity and the sum of n (top) and i=1 (bottom) with (3i/n)^3*(3/n) I don't know how to solve this, can you help me out?