Calculate saving at each level of disposable income and the marginal propensity to save.
a) Saving = Disposable income - Consumption expenditure; Marginal propensity to save = Change in saving / Change in disposable income
b) Saving = Consumption expenditure - Disposable income; Marginal propensity to save = Disposable income / Consumption expenditure
c) Saving = Disposable income + Consumption expenditure; Marginal propensity to save = Change in consumption expenditure / Change in saving
d) Saving = Disposable income - Consumption expenditure; Marginal propensity to save = Disposable income / Consumption expenditure