Feature: Tracing questions

Can we introduce a new kind of problem, tracing where students need to show the steps of evaluation for a given expression like

Trace
4 + 10 - 40

and the students would answer (one line at a time)

=> 14 - 40
=> 26

I think these could not be done programmatically and would just be a lot of grunt work. We don't need like 100 problems in this way, we can start small. It would require just string checking. Maybe it could be a bit more intelligent and notify the student when they "skip" a step along the way or something?