Exam AD0-E718 topic 1 question 5 discussion

An Adobe Commerce Architect is creating a new GraphQL API mutation to alter the process of adding configurable products to the cart. The mutation accepts configurable product ID. If the given product has only one variant, then the mutation should add this variant to the cart and return not nullable Cart type. If the configurable product has more variants, then the mutation should return not nullable ConfigurableProduct type.
The mutation declaration looks as follows:

How should the Adobe Commerce Architect declare output of this mutation?