At the beginning of the school year, 50 \% of all students in Mr. Wells’ math class answered Yes to the question Do you love math, and 50 \% answered No. At the end of the school year, 70% answered Yes and 30 \% answered No. Altogether, x \% of the students gave a different answer at the beginning and end of the school year. What is the difference between the maximum and the minimum possible values of x ?
Answer Choices
A. 0
B. 20
C. 40
D. 60
E. 80