How to handle GraphQL resolvers with an ambiguous parent

I have a schema that looks like the following, each city and town both have unique ID and belong to a state.

type City {
  id: ID!
  population: Int
  name: String
  state: State
}

type Town {
  id: ID!
  population: Int
  name: String
  state: State
}

type State {
  id: ID!
  population: Int
  name: String
}

The queries to fetch the associated info can take either of the following

query getTownAndState($townId: ID!) {
  town(townId: $townId) {
    population 
    name
    state {
      name
      population
    }
  }
}

query getCityAndState($cityId: ID!) {
  city(cityId: $cityId) {
    population 
    name
    state {
      name
      population
    }
  }
}

The resolvers to fetch for either a city or a two are straightforward:

resolvers = {
  Query: {
    city: () => Api.getCity(args.id),
    town: () => Api.getTown(args.id),
    state: () => Api.getState(args.id),
  },

However fetching the city and/or town's associated state is ambiguous because the parentTownOrCity could be either a city, or a town. And the APIs for fetching each respectively is Api.getCity and Api.getTown. Api.getCityOrTownById doesn't exist.

  State: {
    name: (parentTownOrCity) => {
      Api.getCityOrTownById(parent.id); // <-- what goes here?  How to tell if it's a town or a city
    }
  }
}