1. The document discusses consumption, saving, and investment functions. 2. It explains that consumption is a linear function of disposable income, defined as C = C0 + cY, where C0 is autonomous consumption and c is the marginal propensity to consume (MPC). 3. A saving function can be derived from the consumption function as S = -C0 + (1-c)Y, where 1-c is the marginal propensity to save (MPS). 4. Investment is assumed to be autonomous (exogenous) and constant, defined as I = I0, where I0 is a given, positive level of investment.