What is the recommended stock of coal? Which department docs the speaker work in?

M: Jane. shall we go through the inventory then? Let’s start with coal.
F: We have about 45 tons. But we are supposed to have 70 tons.
M: So we’ve got too little. We’d better order some more. How about gas?
F: I think we have enough stock for that.
M: OK, thank you then.

F: In which department do you work?
M: I’m the Production Manager though I also take care of other things such as purchasing, maintenance, quality control and sometimes problems of the staff.