Any such lease contract shall contain an option permitting the State to purchase the lands under lease. The lease contract shall include provisions:
(a)
That all payments made by the State as rental thereunder shall be applied on the purchase price of the lands.
(b)
That at the end of each two-year period, if the State so elects, the lessor will convey to the State, without additional consideration, a designated area of the lands under lease, as described therein, which area shall be such proportion of the total area as the amount of rental paid by the State for such period bears to the total amount of rental to be paid under the lease.
(c)
That the State may terminate the rental contract at its option at the end of any two-year period.
(d)
That the total rental to be paid under any such lease contract shall not be in excess of the appraised value of the lands.