please help me on this question

Assume there are two consumers (A and B) in an economy that have preferences that can be represented as cobbdouglas utility functions. Also assume that there are two firms that have concave production possibility frontiers over goods x and y. Which of the following conditions must be true for an allocation to be pareto efficient? Select all that apply. 3 All producers must have marginal rates of transformation that are equal. 3 All goods in the economy are consumed. 3 All consumers must have marginal rates of substitution that are equal. 3 Producers must be operating on their production possibilities frontier. 3 Consumers must value goods at the margin at the same rate it costs society to produce them