Calculate the class interval of the required class.
 
Class
\(1\)
\(2\)
\(3\)
\(4\)
\(5\)
Interval
9.9 -  16.316.3 - 23.323.3 - 36.936.9 - 49.749.7 - 56
 
The class interval of class \(4\) is .