First you find the concentration of nh4cl and nh3 which is done by converting the amount into litres x by M/the sum of the amounts in litres
so its 0.0579x0.16/0.0579+0.0604. You do this with nh3 as well then the pH is 9.24+log(nh3/nh4)
second part find the moles which is mass/molar mass then...