Find the ith term of the sum. (Let i = 1 be the first term of the sum.) Find the upper bound of the summation when written in sigma notation. Use sigma notation to write the sum.

a) ∑(i=1 to [infinity]) i²
b) ∑(i=1 to n) i²
c) ∑(i=1 to n-1) i²
d) ∑(i=1 to n+1) i²