Description 
The first elasticity tutorial took a qualitative approach to elasticity. The idea conveyed was
Elasticity = Responsiveness
The elasticity of Q with respect to P is the responsiveness of Q to changes in P.
Elasticity has a quantitative meaning, a specific way of measuring responsiveness.
Suppose P changes, and Q changes as a result.
The elasticity of Q with respect to P is the relative change in Q divided by the corresponding relative change in P.
