Miriam consumes tacos and Coke. Suppose the price of a taco is ​$3.80​, the price of a Coke is ​$2.70​, and that Miriam is currently consuming tacos and Coke such that her marginal utility of tacos is 87 and her marginal utility of Coke is 45. Is Miriam behaving​ optimally? If​ not, then what should she​ do?