are you still using 2007
is overtime ONLY at 1.5 times - for any time worked , week, weekend, sunday

how many hours is paid normally ???

what period is the C20 hours worked - for ,

gross pay / hours worked - would give the hour rate

does gross pay , also include the overtime, or is that the base salary ?

i maybe missing something - but can you explain your formula
100+4 ???
e20 *100
i'm not following