It depends on how deep the cake pan is.
1/2 full
15 cups of batter. bake at 325 degrees for 75-85 minutes. Use a baking core.
you put about 1/2 of cake batter
Just fill each pan a little over halfway full so it will have plenty of room to rise
If you are using a 2" deep cake pan you would need 13.5 cups of batter.
As much as you want except if your pregnant
10 Pieces .
6 cups for one layer
5 because the cake swells when it bakes so 5 is enough
It depends on how much of a blueberry flavor you want. For the average amount of cake batter, add about 1 to 1.5 teaspoons of extract.
You should order for only 90% of your guests. Some people will not eat the cake. So again, only order for 90% - in your case that means 12 people or one cake box mix - or one 9 inch round/square cake.