Consider a disk drive with the following specification: 16 surfaces, 512 tracks/surface, 512 sectors/track, 1 kbyte/ sector, rotation speed 3000 rpm. The disk is operated in cycle stealing mode whereby whenever one 4 byte word is ready it is sent to memory; similarly, for writing, the disk interface reads a 4 byte word from the memory in each DMA cycle. Memory cycle time is 40 ns. The maximum percentage of time that the CPU gets blocked during DMA operation is