You'll do it for her
If you do it for her, it is to say, you'll do it for him.
"I can do it for him"
"You'll do it for her"
"Okay, now do that again "
"Yes, ma'am"
"You do it for her, and now you say...."
"I'll do it for him"
"You'll do it for her"
"Okay, now do that again "
"Yes, ma'am"
"You do it for her, and now you say...."
"I'll do it for him"