Pt 3: Kevin is waiter, cook, busboy, and cashier?
In the final act, Kevin says on the phone call to Black he's now a cook. But in the proceeding diner scene with Black, Kevin is the waiter, the cook, the cashier, and the busboy. And he closed shop which would've meant emptying the register and turn down on the kitchen and washroom. We do see a cook (or someone else) when Black first walked in, but they disappeared halfway through. Kevin is quite the Superman to do all that.
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When logic and science aren't on your side, you always lose.