Calculate time periods before and after 7pm

I am making a timesheet for employees which has their start time in B8 and finish time in C8. Because staff are paid a higher rate for working past 7pm I would like to know how to calculate the number of hours worked before 7pm (ie cell C9) and the number after 7pm (ie cell C10). Any suggestions greatly appreciated.

In C9
=IF(C8>19/24,19/24-B8,C8-B8) for the time before 7pm

and in C10
=C8-B8-C9 for the time after 7pm

Thanks for that. Once I formatted C9 and C10 corrrectly (as [h]:mm ) it worked perfectly!