Diesel Bombers

Two couples were playing poker one evening. Jim accidentally dropped some cards on the floor. When he bent down under the table to pick them up, he noticed Bob's wife, Kim wasn't wearing any underwear under her dress! Shocked by this, Jim upon trying to sit back up again, hit his head on the table and emerged red-faced.
Later, Jim went to the kitchen to get some refreshments. Bob's wife followed and asked, 'Did you see anything that you like under there?'
Surprised by her boldness, Jim admitted that, well indeed he did. She said, 'Well, you can have it but it will cost you $500.' After taking a minute or two to assess the financial and moral costs of this offer, Jim confirms that he is interested.
Kim told him that since her husband Bob worked Friday afternoons and Jim didn't, Jim should be at her house around 2 p.m. Friday afternoon. When Friday rolled around, Jim showed up at Bob's house at 2 p..m. sharp and after paying Kim the agreed sum of $500 - they went to the bedroom and closed their transaction, as agreed. Jim quickly dressed and left.
As usual, Bob came home from work at 6 p.m. And upon arriving, asked his wife: 'Did Jim come by the house this afternoon?'
With a lump in her throat Kim answered, 'Why yes, he did stop by for a few minutes this afternoon.' Her heart nearly skipped a beat when her husband curtly asked, 'And did he give you $500?'
Kim, using her best poker face, replied, 'Well, yes, in fact he did give me $500.'
Bob, with a satisfied look on his face, surprised his wife by saying, 'He came by the office this morning and borrowed $500 from me. He promised he'd stop by our house this afternoon on his way home and pay me back.'