After it is determined between the representatives of the employers and the trustees what amount will be contributed for each ton of coal mined and marketed, then blanks for all contracts between the trustees and the employers are to be furnished to the employers, whereby the employers, for a period of at least one year, are to contract with the trustees that they will send to the state treasurer, quarterly, the amount that is agreed upon shall be charged on each ton of coal, for the miners' home or homes, and each succeeding year such amount shall be determined in the same way, and new contracts made.