Calculate task duration minus breaks

Hi, I need to calculate the duration of tasks within a shift minus the lunch and dinner breaks which are at set times, the issue I have is when the task starts after the end time of the break the answer is returned as a negative as seen in F3 in the attached sheet, thanks

Hi
this problem has been asked many times on the board and elsewhere.
Might I suggest you search those two sources first so that our members should not have to waste their time.
Thanks