A、Whether the large order is from a regular client. B、Whether they had the goods in stock. C、Whether the goods can be delivered

W: What did you do at the office today?
M: I had a really busy day. I had to work a little overtime. In the morning an important client called to place a large order. I had to check some things with my colleagues before confirming the order.
W: What kind of things did you need to check?
M: (19) The most important thing was to check whether we had the goods in stock. If the goods are in stock, we can deliver them immediately. I also had to check the price. This customer is very important, so they get special prices.
W: I see. Did anything else happen?
M: I received a lot of emails from potential clients that I had to answer. Each time, I had to check files to see what we had agreed at earlier meetings. Each client has different conditions and requirements.
W: (20) It must be difficult to remember the details for each individual client.
M: Yes. (20) That’s why I have everything on computer files. I don’t use much paper at our office. After lunch, I had to deal with a complaint from a client.
W: I hate dealing with complaints. Was it a reason-able complaint?
M: Yes, it was. I managed to sort out the problem, but I was tied up with the matter for over an hour.
W: You certainly had a busy day.
M: That’s not all! (21) I also had to finish writing a sales report for my boss. In the end, I finished everything. I wonder what will be waiting for me tomorrow morning.
19. What does the man think is the most important thing to check?
20. Why does the man have everything on computer files?
21. What was the last thing the man did?