Depends on the person, but I personally didn't do 2-4 hours per week, out of my own time. I'm the lazy type who never does more than I probably should though, so take it with a grain of salt. You want to be doing at least say 1-2 hours every week, to make sure you're on top of things, but it's unnecessary (imo at least) to put in too many hours unless an assessment is coming up. Keep in mind that at the end of the day, your ext english course only requires you to write one essay and one creative. Ofc you might want to write more than one essay or creative so you can adapt to questions etc (more so for creatives than essays since the questions tend to be quite general), but that's not - or hopefully won't, take you 50-100 hours.
Also, I know you're probably asking this to gauge the amount of effort you'll need to put in, but it's never a good idea to quantify hours since everyone works and have different absorption/learning rates.
Finally, this is something really obvious but I feel like its necessary - your assessments are what counts. Not the amount of effort you put in. So that's to say, it's pointless to put in an hour a day into your ext english if you're neglecting the subject when you have an assessment coming up. I know it seems obvious but you'll be surprised at how many people do that. You really don't want to be that idiot. (-cough- me -cough-)
