A daisy$-$chained I$/$O system receives external interrupts at the following times. Higher numbered interrupts have higher priority.

$\backslash$table$[[$Time$,$Action$],[0ns,$Start of main program$],[10ns,$IRQ$1],[20ns,$IRQ$4],[30ns,$IRQ$2],[55ns,$IRQ$3]]$

This sequence generates the following IACK signals, but there are errors in the values of some of these signals. List three of the $($at least$)$ four errors in the timing diagram and state their corrections.