A processor with a $500MHz$ clock requires $1000$ clock cycles to perform a context switch and start an ISR. Assume each interrupt takes $10,000$ cycles to execute the ISR and the device makes $300$ interrupt requests per second. Also, assume that the processor polls every $0\mathrm{.}5$msec during the time when there are no interrupts. Further assume that polling an I$/$O device requires $250$ cycles. Compute the following:

a$.$ How many cycles per second does the processor spend handling I$/$O from the device if only interrupts are used? $[10$ marks$]$

b$.$ What fraction of the CPU time is used in interrupt handling for part? $[10$ marks$]$