For the Kodak 20 litre packs you need:-
50cc of Concentrate A
24cc of Concentrate B
50cc of Concentrate C
and 80cc of developer starter.
This is for 1 litre of working solution, for 2 litres simply double the amounts.
They must be mixed in warm water (The temp required is on the main instructions supplied) or they do not mix properly.
For replenishment:- (I assume you are using a tank like a NOVA) The dilutions are exactly the same, but miss out the starter concentrate. If you are using a rotational development such as a JOBO, then you will need to use the starter for every mix.
I always store any unused developer in 500cc dark brown glass bottles away from the light and you will find this stays fresh for a long time. I also decant one of these bottles into 5 x 100cc dark brown bottles as I find 100CC is enough for one evening s work so you empty the bottle but the others have little exposure to air and oxidisation.
If you are using a tank like a NOVA, you will find that after finishing for the evening, and replenished the developer and replaced the floating lids. Covering the tank top with 'cling-film' will also help to reduce the onslaught of oxidisation. I have used a NOVA tank with replenished developer for up to 18 months before I had to drain it to get rid of the Tar de[posits