Detailed Instructions: In this task, you need to answer the given multiple-choice question on the general math. Classify your answers into 'a', 'b', 'c', 'd', and 'e'.
Problem:Problem: 1.5 , 2.5 , 4.5 , 7.5 , 11.5 , ( . . . . ) 
Options: a ) 16.5 , b ) 15.5 , c ) 14.5 , d ) 17.5 , e ) 17
Solution:
a