HOW old is mum? is this her first litter? xOtherwise you will be feeding 4 kittens every 2 hours around the clock - seriously. For a good 3 weeks. I still need to tell you how much to feed. Then potty. You'll need to weigh them as I mentioned. Please let me know your thoughts.
Also, you need to get your cat checked at the vet to make sure there is nothing wrong with her.