Being my first time as an owner operator of my own trucking company, ATBS I never heard of before, so understanding what all they really did to help me keep records of my expenses and tax filing was all new to me. as it turns out they were very helpful in the overall operations of my company and glad they were there to help!
My background is not in direct sales, so I had to really stretch to answer this question. Being that the position was for sales support and not direct sales, I thought the interview process would be more accommodating to support roles.
In short, an interface has only the name, parameters, and return types. An interface does not implement these in anyway. An abstract class can do everything an interface does and more, it can define what a method does. Interfaces do not consume the CPU as much as abstract classes because they are only the names for the members to be implemented while abstract classes may have some methods implemented.