What mass of the precipitate is formed when 150.0mL of 0.100 M Fe(NO3)3 is mixed with 200.0mL of 0.200 M KOH? What are the concentrations of all ions that remain in the solution?

I know how get the mass of the precipitate formed, but I can't figure out the concentrations of the ions that remain (Fe, K, NO3) and WHY those remain in the solution. And not OH. If you can answer this question but Don't use the "ICE" method, that would be great. Thank you!