An insured worker's weekly benefit amount is fifty percent of his weekly average wage, as defined in Section 41-27-140, and the weekly benefit amount, if not a multiple of one dollar, must be computed to the next lower multiple of one dollar. However, no insured worker's weekly benefit amount may be less than twenty dollars nor greater than sixty-six and two-thirds percent of the statewide average weekly wage most recently computed before the beginning of the individual's benefit year.