(3) If the landlord fails to carry out the duties imposed by RCW 59.18.060 within the applicable time period, and if the cost of repair does not exceed one month's rent, including the cost of materials and labor, which shall be computed at the prevailing rate in the community for the performance of such work, and if repair of the condition need not by law be performed only by licensed or registered persons, and if the tenant has given notice under RCW 59.18.070 , although no estimate shall be necessary under this subsection, the tenant may repair the defective condition in a workmanlike manner and upon completion of the repair and an opportunity for inspection, the tenant may deduct the cost of repair from the rent. Repairs under this subsection are limited to defects within the leased premises. The cost per repair shall not exceed one month's rent of the unit and the total costs of repairs deducted in any twelve-month period under this subsection shall not exceed one month's rent of the unit. (4) The provisions of this section shall not: