Option 2: (A), (C), (B), (D) -> The correct chronological order for determining equilibrium income starts with the equilibrium condition Y = C + I, then substituting the given values to get Y = 50 + 0.8Y, followed by rearranging to isolate Y terms as 0.2Y = 50, and finally solving to get Y = 250. This follows the logical sequence of: stating the equilibrium condition → substitution → algebraic rearrangement → final solution. -> correct