A Washington statute provides that whenever the public service commission shall deem it necessary in the performance of its duties to make any investigation or valuation of a public service company, the public service company shall pay the expenses reasonably attributable thereto. The statute provides that the commission, after giving an opportunity to be heard, "shall render a bill therefor or for such part thereof as it may find necessary and reasonable." In an appeal by certain public service companies from an assessment made by the commission, held, the statute was unconstitutional because of denial of equal protection of the laws and also because it contained an unconstitutional delegation of legislative power since it set forth no standards but authorized the department to charge to the utility all or any part of the expenses of the investigation as it might consider "necessary or reasonable." State v. Northwestern Electric Co., 183 Wash. 184, 49 P. (2d) 8 (1935).