Thor,
Yes, I had already noticed this. The issue is caused by the use of an internal function "logbase", rather than the function a student types in. This will be resolved in the next version. There will be no need to use logbase at all. Just use lg(x) for log to the base 10, and lg(x,n) for a general logarithm. The "teacher's answer" as you show above, will reflect this change.
Chris