Upon the filing of the petition with the county assessor that officer shall proceed forthwith to conduct such investigation as may be necessary to ascertain and determine whether or not the assessment in question was erroneous or whether or not the tax was incorrectly extended upon the tax rolls and if he or she finds there is probable cause to believe that the property was erroneously assessed, and that such erroneous assessment was due to an error in description, double assessment, or manifest error in assessment which does not involve a revaluation of the property, or that the tax was incorrectly extended upon the tax rolls, he or she shall endorse his or her findings upon the petition, and thereupon within ten days after the filing of the petition by the taxpayer forward the same to the county treasurer. If the assessor's findings be in favor of cancellation or reduction or correction he or she shall include therein a statement of the amount to which he or she recommends that the assessment and tax be reduced. It shall be the duty of the county treasurer, upon whom a petition with endorsed findings is served, as in RCW
84.68.110 through
84.68.150 provided, to endorse thereon a statement whether or not the tax against which complaint is made has in fact been paid and, if paid, the amount thereof, whereupon the county treasurer shall immediately transmit the petition to the prosecuting attorney and the prosecuting attorney shall make such investigation as he or she deems necessary and, within ten days after receipt of the petition and findings by him or her, transmit the same to the state department of revenue with his or her recommendation in respect to the granting or denial of the petition.