Singular or plural following a list
James and Mark are going to help you.
Here, I use 'are' because the subject is plural.
James or Mark are going to help you.
James or Mark is going to help you.
Here, I’m not sure whether to use 'are' or 'is' because the subject isn't plural(?) It’s one or the other – so does that mean the subject is still plural, and I should use 'are', or is 'is' correct here?