Lessons

The hours nobody paid you for

What it is
Your contracted hours, plus the ones you actually work on top of them, plus the commute if you count it as sold time.
Why it matters
Your contract sets your pay. Your real hours set your rate. The difference between the two is the quietest pay cut there is, because nobody announces it and it never appears on a payslip.
The method
Contracted hours a week, honestly. Then the extra: the staying late, the work carried home, the messages on Friday night. Commute is yours to decide — it is time you cannot sell to anybody else.
Example
Salma is contracted for 40 hours. Marking and parent calls add about 15. On paper she earns PKR 484 an hour. On 55 hours she earns PKR 352.

Now you

Contracted hours a week, extra hours a week, and the commute if you count it.