Assume that three I/O devices are connected to a 32-bit, 20 MIPS CPU. The first device is a hard drive with a maximum transfer rate of 2MB/sec. It has a 32-bit bus. The second device is a floppy drive with a transfer rate of 50KB/sec over a 16-bit bus, and the third device is a keyboard that must be polled forty times per second. Assuming that the polling operation requires 30 instructions for each I/O device, determine the percentage of CPU time required to poll each device.