There's a builder working on a room in downstairs of the house. It's a hot day. The house is old and has thick stone walls so stays quite cool in summer.
The builder wants to prop the back door open as he is coming in and out every few minutes with wheelbarrows/tools/buckets etc.
Person A wants the builder to open and shut the door behind him every time he needs to go in or out to keep the house cool. This is not without merit, as the house does stay a bit cooler with the door shut.
Person B thinks the builder should be allowed to leave the door open because it makes his work much easier and if he is doing manual labour on a day like this then his clients should be doing everything they can to make his work easier, including putting up with the house being a bit warmer than it would be otherwise.
Who is BU?