City take on Arsenal at Wembley on Saturday evening before United face Chelsea a day later.If both City and United win, they will face each other in a final at Wembley to be played in August.With the Premier League having altered its substitution rules in order to alleviate the strain on players who are in the middle of a hectic schedule due to the coronavirus, many fans will be wondering whether the FA Cup has followed a similar solution.Here are the important rules you need to know for the