(a) Lessees shall pay, in addition to other considerations, annual advance rentals as follows: 15 cents per acre for the first year; 30 cents per acre for the second year; 50 cents per acre for the third year; and $1 per acre per annum for the fourth and each succeeding year during the life of any lease: Provided, That all such payments of advance rentals shall be credits on royalties on production during the year for which payment of advance rental is made.

(b) The payment of annual advance rental shall not release the lessee from the obligation to conduct mining operations, as required by the terms of the lease.