Who most likely is Jack?

M: You didn’t forget to call the Maintenance Department to take a look at our machine, did you?
W: I made the call to Jack as soon as I got into work at 9 this morning,(65)but he said he had many rounds to make today.(66)According to him, the earliest he can come is around 4.
M: That’s a bit late. I have an appointment with Mr. Smith at 5, and it will take me at least an hour to get there.(67)We need someone here to explain the problem to him.
W: My meeting with my client got canceled. I’ll stick around and tell Jack about the problem. You go right ahead and meet Mr. Smith.