When land has been sold on contract as provided in this chapter and the purchaser, or the purchaser’s heirs or assigns, have been unable to pay for the land purchased within twenty years after the date of purchase and such contract is in default and subject to cancellation, and when such inability to pay under the contract has been caused in whole or in part by reason of successive crop failures, the board of university and school lands, if requested so to do by such purchaser, or the purchaser’s heirs or assigns, after it has declared such contract terminated, may resell the land described therein to such purchaser, or to the purchaser’s heirs or assigns, for the amount of the unpaid principal of the original purchase price plus the amount of unpaid accrued interest, but in no case may the resale price be more than the original sale price. Upon such resale, a contract of resale must be issued to the purchaser upon the same terms as were contained in the original contract except that the contract of resale may provide that the purchaser may pay the first one-fifth of the resale price in five equal successive annual installments, the first to be paid at the time of execution of the contract, and that such contract shall bear interest at the rate of three percent per annum payable annually.