One way to approach this problem without using a calculator is to group the numbers by their place value (i.e., thousands, hundreds, tens, and ones), and then add them together.
For example,
For thousands:
User A has 3 thousands,
User B has 4 thousands,
User C has 2 thousands,
User E has 7 thousands.
There are no thousands for User D.
So the total number of thousands is 3+4+2+7 = 16 thousands.
For hundreds:
User A has 550 hundreds (since 3550 = 3 x 1000 + 550),
User B has 0 hundreds (since 4000 is a multiple of 1000),
User C has 450 hundreds (since 2450 = 2 x 1000 + 450),
User D has 10 hundreds,
User E has 0 hundreds (since 7000 is a multiple of 1000).
So the total number of hundreds is 550+0+450+10+0 = 1010 hundreds.
For tens and ones:
Since all the numbers are in thousands or hundreds, there are no tens or ones to add.
Therefore, the total amount of data stored on the server is:
16 thousands + 1010 hundreds = 16,100 GB