Which of the following statements is true?

1- if demand is linear, slope will very across different points on the demand curve whereas the elasticity will be the same at all points in the curve.

2- Elasticity does not depend on units whereas slope does

3- The data needed to know the demand curve's entire slope are more likely to be available than the data needed to calculate elasticity at a given price

4- Price elasticity of demand and slope are two names for the same concept