This is related to Partnership

Mark, Lennie and George are friends who fly model aeroplanes in the weekends at a model aeroplane club. Mark has good technical skills and can assemble and repair the model aeroplanes. Lennie is an accountant and has good business skills. George is a happy person who makes friends easily and is good at persuading people to do the kind of things he likes doing. Mark has been assembling and repairing model aeroplanes for other club members in his garage at home. He has to buy spare parts for the repairs and he resells the parts to the club members when the repair is complete. Lennie starts helping him to keep control of the payment of the expenses and the collection of the money. Being an accountant, Lennie persuades Mark to start charging for his time and trouble, and to add some more to his charges so Lennie can get paid for the accounting work.

George hears about this and starts bringing along people from his wide circle of friends to be introduced to model aeroplane flying and to get Mark to assemble their planes for them and to keep them in good repair. George also wants to be paid so that he can buy better aeroplanes for himself and his twin sons. They decide that the easiest way is to increase the fees that Mark is charging and for the three of them to share what is left over after paying for the costs of the parts and a small rental to Mark for the use of the garage. Lennie has discovered a good source of new model aeroplanes in Korea and starts importing them to resell through Marks garage workshop, sharing the markup with the others.

Does a partnership exist? Who are the partners?