How can I use 'withDefaults' to define default values for multi-layered objects

[zzw105]

interface propsType {
  obj?: {
    a?: number
    b?: number
    c?: number
  }
}

const props = withDefaults(defineProps<propsType>(), {
  obj(props) {
    return {
      a: 200,
      b: 71,
      c: 160
    }
  }
})

console.log(props.obj.a)

https://play.vuejs.org/#eNp9kstqwzAQRX9FaJVAsJMGWjBOSh9ZtIs2tFlq48fYUSpLQpLzIOTfO7ZiNy0lYMzcuSPN0UhH+qB1sK2BRjR2UGmROJgzGed8O4/D5o8ivHBQ2sxw7YgFV2siElnOGHWW0dbl0oEpkgyINkrb1UEDOTJJiEo395EPCUkwlHWVgvE6/aOzX/rEJH5MZkpa5/clM7Ljbv0MRVILZwc5FFzCsrHivvF8MBz1zQdtetgRGKQ3slNIFJGb8XjUyTQid5NeZRGZ3I69QhJPNOyQlIBAqNI3CLBVkKAXh35O55m5gwBiM6UhJz4VtjmM6QjHhxsVvAw2Vkm8ixaL0UxVmgsw79pxbMRoP0BGEyHU7rXNOVPDmRXXrCH7+ie/sfsmx+jSgAWzBUZ7zyWmBOftxecb7DHuzUrltcDqK+YH4BDqhtGXPdYyR+yLupb2pdLKOC7LlV3sHUjbHaoBbcfa1jOKD/LpytF/cKfBtLsOevoG8JPrUA==

How can I add default values to a