The task is to generate the correct answer for a given math problem.

Problem: the curved surface of a sphere is 64 π cm 2 . find its radius ?
4', 'd ) 9', 'e ) 7'

Problem: a certain experimental mathematics program was tried out in 2 classes in each of 38 elementary schools and involved 44 teachers . each of the classes had 1 teacher and each of the teachers taught at least 1 , but not more than 3 , of the classes . if the number of teachers who taught 3 classes is n , then the least and greatest possible values of n , respectively , are
0 and 16

Problem: carolyn bought 17 gumballs , lew bought 12 gumballs , and carey bought x gumballs . the average ( arithmetic mean ) number of gumballs the 3 bought is between 19 and 25 , inclusive . what is the difference between the greatest number and the smallest number of gumballs carey could have bought ?

18