Finding the lower bounds of an algorithm I am struggling to calculate the lower bounds of an algorithm. What is the right way to proceed.

For eg, I have the following algorithm

For i=1, 2,...,n
    For j=i+1, i+2,...,n
        Add up array entries A[i] through A[j]
    Store the result in B[i, j] Endfor
Endfor


How do I calculate the lower bounds of this algorithm
Hint: The complexity is proportional to the number of reads from the array $A$.