Which of the following is true?

1. Marginal propensity to consume shows the change in consumption as a result of a change in disposable income.
2. Independent consumption increases as a result of an increase in the general price level
3. Independent consumption increases as a result of a decrease in the real interest rate.
4. Disposable income increases as a result of an increase in lump sum taxes.
5. Both a and c.
6. Both b, and c.
7. All.