4. Consider a consumer with the following utility function: u(x,y) = (x + y? ) [where p is a constant parameter] and budget constraint: P, x + p,y = m a) Derive the optimising condition that the marginal rate of substitution between the two consumption goods equals their price ratio. b) Solve for the consumer's ordinary/Marshallian demand functions. c Derive the indirect utility function. d) Formulate the dual version of this problem (cost minimization problem) and derive:: i. Hicksian demand functions: ii. Indirect expenditure/cost function