Basic hours/salary and extra hours on the salary calcutation

It would be great for me and others I think.

For example:

Salary is 20£/h for minimum 10h(or any time) work time (10hx20£=200£). If i work 5 (up to 10h) hours per shift/day/week i get 200£. Over that basic hours salary can be 25£/h.

When if i work 12h per shift salary will be 10hx20£/h+2x25h=250£ for 12h

If I work 8h per shift salary basic