Consider the question. The longest-serving and most successful person to manage Manchester United is Sir Alex Ferguson, who won 13 Premier League titles, five FA Cups, four League Cups, 10 Community Shields, two UEFA Champions League titles, one UEFA Cup Winners' Cup, one UEFA Super Cup, one Intercontinental Cup and one FIFA Club World Cup in his managerial reign of more than 26 years.

Who is the longest serving manager in man united?
If the answer is 'Sir Alex Ferguson'; explain the reasoning:
To answer the question, consider the following: The longest-serving and most successful person to manage Manchester United is Sir Alex Ferguson, who won 13 Premier League titles, five FA Cups, four League Cups, 10 Community Shields, two UEFA Champions League titles, one UEFA Cup Winners' Cup, one UEFA Super Cup, one Intercontinental Cup and one FIFA Club World Cup in his managerial reign of more than 26 years.