How do you calculate overtime pay on excel?

Example:

Enter in cell:

A1 - Rate of pay

A2 - Hours worked

A3 - =(A2-8)

A4 - =(A1*8)+(A1*1.5*A3)

I double time is involed use A1*2 in Cell A4

This formula can be shortened but this is the simplest way I know.