help

You can always use shoelace formula. I'm a little lazy today but I will provide you a resource:

https://www.youtube.com/watch?v=Ow24sLQXokU for shoelace formula

Thanks AELN

 

I think resource links like this are better than actual answers to specific problems. 

 

I would just suggest that you use the link button though. It just makes it easier for the user.