If checkbox is checked, display a number

Hello!

I'm looking to format some cells, but I don't know if it can be done.

For every box that is checked in B-D, I want 'total' to add 25. IF box E is filled, I want it to remove 25.

For example, if B and C is checked, show '50'. If B, C and D are checked, show '75'. HOWEVER, if B and E are checked, it would show 0.

I'm happy if I have to separate it out, for example have a total and then a second box saying if x is checked, display total-25.

Does anybody have any idea how to do this please?