Find large or max with logical values

I have a set of alpha numeric values in a scale 3c,3b,3c,4c,4b,4a
I want to be able to add a formula in the next column to return the largest value.
I thought either max or large could be used to return a value but neither work on logical values.

I cant convert the values numbers to a number only.

I would use an if statement but this would get very large (there can but multiple columns to check)

anyone have an idea?