A、They had different business strategies. B、Customers often mistook one for the other. C、Conflicts between them could not be pro

W: So John, I hear you and Arthur share a job, don’t you?
M: Yeah. (19) We’ve shared a sales job at Sonatech for about two years now.
W: Well, how do you divide up your schedule?
M: (19) You know we are both sales representatives and we take orders over the phone. When we started job sharing it was difficult, because we both worked all day Monday. I worked Tuesday and Thursday and Arthur worked Wednesday and Friday. (20) The problem was that when I was in the office on Tuesday, I would talk to people. Then they would call back on Wednesday with a question. But Arthur couldn’t answer the question and he couldn’t ask me about it because I wasn’t in the office. So he had to ask the people to call me back the next day, Thursday. Of course, they didn’t like to wait until the next day to have their questions answered.
W: Yes, that sounds like a problem.
M: So, finally we decided that Arthur would work in the mornings and I would work in the afternoons. Now if someone calls with the question for me in the morning, Arthur tells them to call me in the afternoon. This way, people get their questions answered the same day.
W: What do you do about vacations?
M: Well, (21) Sonatech gives the usual two weeks of vacation to full-time employees. I take a week and Arthur takes a week.
W: It sounds like job sharing has worked out well for you.
M: Yes, it has. We are both happy with it.
19. What do John and Arthur do at Sonatech?  
20. What problem did John and Arthur have when they started job sharing?
21. What does John say about their annual vacation?