What is the interaction activities between the QC and QA engineers?

Quality Assurance is more process driven. This means that there are a set list of procedures that help to maintain a high level of quality. If followed, theses procedures eliminate unnecessary mistakes before making something. Quality Control can best be explained as capturing defects and non-conformance before they get used or shipped. This is often done by testing (FAT = Factory Acceptance Test) or measuring by quality control personnel to make sure items are with in specified tolerances (on a machined part, for example).

So, in short, Quality Assurance is geared to catching mistakes before they happen.Quality Control is catching them after they happen and before they get to the client or end user. I hope to clarify their individual activities.