At the start of the second half, the match was decided when Mohamad Salah made it 2-0 on penalties.
Luis Diaz got between two Rangers players and when he felt the contact he fell and settled the penalty.
Salah hit it in the middle of the goal as 40-year-old Allan McGregor dived into the right corner.
Sir Alex Ferguson quietly took a sip of coffee in the stands.
Already after seven minutes, Liverpool took the lead 1-0 on a free kick.
Four Liverpool players stood and discussed with their hands over their mouths before Trent Alexander-Arnold clipped the ball in near the left-hand cross after a wonderful strike.
80-year-old Sir Alex Ferguson coached Manchester United between 1986 and 2013. He was born in Glasgow and played with Rangers between 1967 and 1969.