By Katie Catherall Alejandro Garnacho and Kobbie Mainoo became the first teenagers to score in an FA Cup final since Cristiano Ronaldo in 2004 after earning victory over Manchester City on Saturday. Garnacho was the first to find the net, putting his side ahead on the 30 minute mark. The lead remained in the hands of the Red Devils and was soon doubled as Mainoo made it 2-0 just 9 minutes later. A strike came from City’s Jeremy Doku in the latter stages of the game, but United remained composed until the final whistle. Two of Erik ten Hag’s youngest players proved to be the most vital at Wembl…