As a teacher myself I can fully understand your wariness of faulty equipment. Preparing a lesson that is suddenly rendered redundant because the laptop powering the projector malfunctions is a needlessly stressful situation. And quite why being able to teach should somehow involve a detailed knowledge of Apple's returns and refunds policies is beyond me - perhaps they do things differently in America. The point of a forum is that it's a community of generously-spirited people willing to be helpful and answer questions such as these. Sadly, however, they're also home to people sniffing round for any opportunity to look smart at other people's expense. Mistrust anyone who invokes 'common sense' to back up their particular perspective: Einstein called it all of those petty prejudices you inherit from your parents and fail to shake off by the time you're eighteen. Or something like that. It's usually a sign of an inability to think outside of received world-views.
Don't presume we all adopt this same snarky tone or approach.