Answer:
In the number of days unpaid column (E8), input the formula; "=DAYS(D8, C8)" then copy it down to the last item on the table.
Explanation:
Answering just the first question, the DAYS function is used to calculate the difference between day timelines. The function accepts two parameters, the first date which is the current date we are subtracting from, and the second date which is the previous date.