See I got it wrong for two reasons:

I was a knuckle head and missed the "English only" so yes varchar or char. The choice between the two though, to me, is subjective. Yes VARCHAR's do require an additional 2 bytes as length identifiers (remember VSAM? lol). I question is "Their length will vary from seven to ten characters" ... "with an even distribution of lengths" "Since the average size of the data is 8.5". We can't store data in half bytes (unless you are working with assembler. remember 3270 ASM?). In fact we can't store data in perfect little bytes. There are 32 or 64 bit WORD boundaries. For me 8, 12, or 16 would have been more efficient, but that's just the hardware nut in me.