(a) The contract must require the payment of the deposit in installments as agreed to by the parties. The last installment must be paid not later than three years from the date of the contract.
(b) The parties may contract for the installments or the amount due to be evidenced by negotiable certificates of deposit or cashier’s checks, payable at specified dates.

(c) The contract must set the rate of interest applicable to the funds placed in the special depository under this subchapter unless the parties agree that the funds are not to bear interest.