What is the main topic of the conversation?

M： I’ve received some information about a convention in London next month, I can’t go, but maybe you’re interested.
W： What’s it about? I’d like to go if the event is on marketing.
M： Oh, sorry. I should have mentioned that, yes, it’s a sales and marketing event.
W： Does it say who’ll be presenting?
M： Let’s see. I have the invitation here... Um...Keynote speaker...Jack Holland, I’ve never heard of him.
W： He’s a professor at Greggory University. I took one of his courses years ago. He’s very interesting so I think I might go.
Number 41.What is the main topic of the conversation?
Number 42.What does the man mean when he says, "Let’s see"?
Number 43.Who is Jack Holland?