Out of the given options, choose the one which is the correct indirect speech of the sentence given below.
"Let us invite some friends to our son's birthday", said the father.
1
The father proposed that they should invite some friends to their son's birthday
2
The father proposes that they could invite some friends to their son's birthday
3
The father proposes that they can invite some friends to their son's birthday
4
The father proposed that they will be inviting some friends to their son's birthday