Whenever a member’s contribution rate is temporarily reduced by statute, a memorandum of understanding, or the Director of Human Resources, those reductions shall be limited to the payment of member contributions during the reduction period and do not apply to the purchase of service credit or the redeposit of member contributions. The purchase of service credit and the redeposit of member contributions shall be subject to the normal rate of contribution for the member in effect immediately prior to the temporary rate reduction.