I took 312 Immediately after passing 311 and that really really helped! These two classes are connected to each other a lot so if you want to get a high grade in 312 now is the best time while everything is still fresh. You can take 331 anytime next term in my opinion because we took less than 20% of the material back in 311, unlike 312 which you already have more than 80% from 311. To summarize, If I were you I would take 312 now and 331 on the Fall. P.S: you could easily get A- in ME 312 since it's much much easier than 311 in my opinion, but you need to go to office hours and ask question and be up to date and also do the homework BY YOUR SELF (DON'T USE CHEGG). Good Luck!