28. The demand for good X has been estimated by Qxd=12-3Px + 4Py. Suppose that good X sells at $2 per unit and good Y sells for $1 per unit. Calculate the own price elasticity. a) -0.2. b) -0.3. c) -0.4. d) -0.6. 29. For the demand function shown below, if the price of the good is $40, what is the consumer surplus? SP 90 80 70 60 50 40 30 20 10 D a) $45 b) $1800 c) $50 10 20 30 40 50 60 70 80 90 d) $1125