A cell phone company has a program which encourages consumers to turn in their old cell phones rather than throw them away when they are finished with them. This is an example of:

Trade will take place: a. if the maximum that a consumer is willing and able to pay is less than the minimum price the producer is willing and able to accept for a good. b. if the maximum that a consumer is willing and able to pay is greater than the minimum price the producer is willing and able to accept for a good. c. only if the maximum that a consumer is willing and able to pay is equal to the minimum price the producer is willing and able to accept for a good. d. none of the above.