For workings (2), Division B Is able to produce 200,000 sets of fittings. The maximum external demand is 180,000 sets, which leaves 20,000 sets available to sell to Division A.
For workings (3), Division A produces 80,000 baths and therefore needs 80,000 sets of fittings. They will get 20,000 from Division B (as per workings (2) ) and the remaining 60,000 externally.