Gdefine memory hierarchy. a. the rate at which information can be transferred from one place to another. b. ordering storage systems according to their speed, capacity, and cost. c. when the cpu tries to read from a memory location and it has to wait for the information to be retrieved from main memory. d. an i/o device, such as a keyboard, that is used to control a computer. e. a circuit that interfaces between a peripheral device and a bus connected to the cpu.