Is dealing with a fixed profit margin on capital in car rental investment contracts considered usury, and what should the accountant do about it?

For investment in any company to be permissible, the following conditions must be met: the field of investment must be permissible (halal), the capital must not be guaranteed but rather be subject to profit and loss, and the agreement must be on a known percentage of the profit, not of the capital. Any guarantee of capital or agreement on an amount attributed to capital invalidates the partnership by consensus. One must disregard the capital when distributing profits, as focusing on it leads to the legal invalidation of the partnership. If the profit is not known, this indicates that the company distributes profits based on the investor's capital, which is forbidden, corrupts the partnership, and is a stratagem for usury. In this case, it is not permissible for you to account for these profits or assist in them.