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1. [15 marks) A consumer has preferences over consumption today (21) and consump- tion tomorrow (22) given by: u(21,22) = x122 Suppose R1 = 60 and R2 = 30. a. Suppose the interest rate, r, is 0.1 (i.e. 10%). Calculate the consumer's optimal savings or borrowing. b. Suppose now rb = 0.1 (the rate of interest on borrowing), but rs