A small trader works with a big trader in car business. The latter deals with the former according to the following mechanism:
The small trader is given the right to sell a certain car within a period of one month in return for a thousand JDs given to the big trader as guarantee against any future loss resulting from this transaction. The small trader tries to sell that car within that period, and whatever profit he manages to make is his. If he makes no profit, he gets nothing, and when that car is sold for less than a thousand from its market price, he loses the thousand, which he had already paid. In addition, the big trader, so as to bear no loss, has the right to sell the car immediately in case its market price drops. If the month ends, the car is either sold for its market price, or the small trader pays another thousand to extend that deal for another month, and the car remains at the big trader`s dealership where he takes care of it in return for fifty JDs. What is the ruling of Sharia on this?