Four numbers are written in a row. The average of the first two is $21$ , the average of the middle two is $26$ , and the average of the last two is $30$ . What is the average of the first and last of the numbers? (2022 AMC 8 Problems, Question \#16) 
选项为:A:$$24$$  B:$$25$$  C:$$26$$  D:$$27$$  E:$$28$$  请回答其中一个选项.