Please answer all of the questions because its all a whole part of question

3. a) Why the firm should monitor accounts receivables? b) Assume that a particular lockbox of a firm receives an average of $75,000 per day in receipts, business days are 250 days. In this situation, ' A depository transfer check would cost $1.5 and provide two-day availability . ' ACH electronic transfer would cost $3.00 and provide 1 day availability, and ' A wire transfer would cost $16.00 and provide 0.5 day availability. ' The required return is 8% per year. Calculate the total transfer cost and determine which mechanism is to be used