A computer system has enough room to hold four programs in its main memory. These programs are idle waiting for I/O half the time. What fractions of the CPU time is wasted? Consider a swapping system in which memory consists of the following hole size in memory order: 10KB, 4KB, 20KB, 18KB, 7KB, 9KB, 12KB, and 15KB. Which hole is taken for successive segment request of (1) 12 KB, (2) 10KB, (3) 9KB, for a. First-fit? b. Best-fit c. Worst-fit