The schedule of premiums to be charged eligible individuals for a benefit plan must be established by the lead carrier and approved by the board, but may not exceed one hundred thirty-five percent of the individual premium rates charged for similar coverage throughout the state. If similar coverage is not offered by other insurance carriers, premium rates for actuarial equivalent benefit plans offered by other insurers in the state must be provided by the commissioner and utilized by the lead carrier to determine association rates for the benefit plans.