A program contains a while loop whose each iteration reads one integer from a long file of integers on the

disk. The file of $32-$bit integers is of size $64$Mbytes. The while loop terminates when the end of the file has

been reached. Excluding time waiting on the disk, each iteration of the while loop takes $120$ cycles on

average. The file is read using a file$-$read system call that returns the next integer one at a time. Internally,

for efficiency, the file$-$read system call reads in one track $(128$Kbyte$)$ of data at a time into an internal buffer

that is invisible to the caller. When the buffer becomes empty, the next sector is read. The time to read a

track from the disk is $800,000$ cycles.

$($a$)$ How many track reads does the program do using the system call?

$($b$)$ What is the total time for computation only, excluding disk $\frac{\text{I}}{O}?$

$($c$)$ Assume that all the other tasks that the program is running take an insignificant portion of the CPU's

time. What percentage of the program's total wall$-$clock execution time is spent waiting for the

disk?