$*$please explain in detail to understand$*$

Given the following set of events, show which routines the CPU is executing for

times $0$ to $100$ ns $.$ Each handler routine $($with its interrupt request$)$ takes $20$ ns to

complete. The priority of the interrupts ranges from IRQ$6$ as the highest priority

interrupt to IRQ$0$ as the lowest priority interrupt.

Time ${?}_{(}())$

Action

$0$ ns: $,$ Start of Main Program

$10s$:$,$ IRQ$1$