I have the following two interfaces **that cannot be modified**:

```
interface User {
  username: string;
  email?: string;
  age?: number;
  country?: string;
}

interface Player {
  room: number;
  group?: string;
  device?: string;
}

```

I want to combine them into just one inteface: `Member` and at the same time making the fields: `User['email']` and `Player['group']` mandatory (just those 2).

I tried the following (just as an starting point (TBD)):

```
// please edit this code accordingly
interface Member extends User, Player  {}

```

Then, the expected result is to get an error on:

```
const member: Member = {
  username: 'bill.gates',
  // email: 'bill.gates@microsoft.com',
  age: 50,
  room: 5,
  // group: 'A',
}

```

since `email` and `group` are not specified.

Here you have a [Playground](http://www.typescriptlang.org/play/#code/JYOwLgpgTgZghgYwgAgKoGdrIN4ChnICumUIcAthAFzLphSgDmA3PshOXMADYD8NdBiBZs4jCP2QhC5AEbRWBBAHtC4KAE9JgpqwC+uXKEixEKAArc4GrHgJRly8jWlyFbRg8IAHbfV1sACYQAG7ASH5CIgZG4NDwSMgAshzyUOwAHpAggehoJAA0yJbWWDgxKiB0yJRuUDQpdcgAvDhsxNBklDQA5LI83AB0jHCQ6D0FbAD0U+ycPL393EMjYwAC5OEO6MowYIMq5BOi4jQArAAMk-aOzshn18gzyJ6q3r0AgscGQA).

Thanks!