Each member of the senate or house of representatives when serving on official legislative business shall be entitled to receive, in lieu of per diem or any other payment, for each day or major portion thereof in which he or she is actually engaged in legislative business or business of the committee, commission, or council, notwithstanding any laws to the contrary, an allowance in an amount fixed by the secretary of the senate and chief clerk of the house, respectively, in accordance with applicable rules and resolutions of each body. Such allowance shall be reasonably calculated to reimburse expenses, exclusive of mileage, which are ordinary and necessary in the conduct of legislative business, recognizing cost variances which are encountered in different locales. The allowance authorized shall not exceed the greater of forty-four dollars per day or the maximum daily amount determined under RCW
43.03.050, as now or hereafter amended. In addition, a mileage allowance shall be paid at the rate per mile provided for in RCW
43.03.060, as now or hereafter amended, when authorized by the house, committee, commission, or council of which he or she is a member and on the business of which he or she is engaged.