We want to calculate what is the relationship between the amount Diego collected and the amount Carlos collected. To do so we will calculate the ratio of Diego's quantities and CArlos' quantities.
For example, note that for the first month we have

for the second month, we have

for the third month we have

We can check that for each month we have that the quantity Diego collected divided by the quantity Carlos collected would give a ratio of 4.
This means that Diego collected always 4 times more than Carlos