Hello, I am really in need of help right now!

I have an accounting exam in about 5 hrs and I need to know how to solve problem for reference to the exam. Please answer ASAP!

Harrti Corporation has budgeted for the following sales:

July$447,000

August$582,000

September$616,000

October$891,000

November$740,000

December$700,000

Sales are collected as follows: 20% in the month of sale; 55% in the month following the sale; and the remaining 25% in the second month following the sale. In Razz's budgeted balance sheet at December 31, at what amount will accounts receivable be shown?

The answer to this is 745,000 and the solution is this:

December sales accounts receivable ($700,000 80%)$560,000

November sales accounts receivable ($740,000 25%)185,000

Total accounts receivable$745,000

My question here is how did they get those percentages since they are not the percentages from the sales? Please explain as clearly as possible and with detail :)