Calculating overtime

Hi Gurus,

I've been trying to work on this formula for quite some time already, but unable to get it working correctly. Sorry, I'm not very good a programming. Anybody can help me to look into this formula to calculate overtime?

For example:
The overtime hour will always start after 5.30pm

Ever 15 minutes, it's counted as: 0.25 hours.

The time for overtime is always round down, for example:
5.30pm to 6.48pm (6.48 round down to 6.45) = 1.25 hours
5.30pm to 7.14pm (7.14 round down to 7) = 1.50 hours
5.30pm to 8.33pm (8.33 round down to 8.30) = 3 hours

In the end of a week or so, there will be a total of overtime hours for that week.

For example:
1 hour of overtime = 11 dollars
total of overtime hours x 11 = ....

From the above example: 5.75 (total overtime) x 11 = 63.25

How would I be able to calculate this overtime working hours correctly?

Would appreciate for any of your help and advice.

Thank you.

- Jack