For the various SCADA subsystems below, how would you rank their task levels? Please arrange them in descending order of priorities giving explanations, i$.$e$.$ the most important subsystem first and the least important subsystem last.

$1)$ Automatic Generation Control

ii$)$ System Scan

iii$)|$ Man Machine Interface

iv$)$ Security assessment

v$)$ CRIT$/$VDU display

vi$)$ Data logging

vil$)$ Event logging