I would tell the ignorant doctor following things about the vitamic C in the short run and long run That the price of vitamin see is going to be inelastic because there are lot of companies manufacturing it and that the product is homgenous and will have inelastic nature in the short run According to the study if the future demadn will increase for vitamin C then the price will likely tor ise up and also the vitamin C can be supplied to the customer in many way or form like in form of organic juice , tbalets or pills, drinks etc so the coming future of vitmain C is bright In the long run , the adult condition as degrading due to changing work culture and high busy life in which 500 mg can provide them with a lot of benefit so in long term the vitamin C mmight be elastic in nature