Given the task definition and input, reply with output. In this task, you need to provide the correct option for a given problem from the provided options.

Problem: in a class of 25 students , 15 play hockey and 16 play basketball . if there are 4 students who play neither sport , determine the number of students who play both hockey and basketball ?
Options: a ) 10 , b ) 11 , c ) 13 , d ) 14 , e ) 15
a