Farmer's reducer is:
Farmer's Reducer is composed of separate solutions of Potassium Ferricyanide and Sodium Thiosulfate (plain hypo). These are usually combined just before use or are used as a two bath treatment.
Potassium sulfite + Sodium sulphate
Potassium ferricyanide + Sodium thiosulphate
Potassium sulfite + Sodium hydroxide
All of the above