Agirl tells her mother she is volunteering at an animal shelter because it makes her feel good, but the truth is that she has been offered extra credit in one of her classes to do so. her motivation is

The better grade.
She is not doing the volunteering to help. She is being motivated by the extra credit that is helping to bring up her grade. If for example, the teacher said she won't get extra credit whether she volunteers or not, there is a higher probability that she won't volunteer. 

Their are ways that keep us inspired and motivated in doing some work and most of all we do this because we gain something that may help up or either its our responsibility to do it or its just for other person. The motivation that the girl to volunteer to the shelter is the Extra Credit.

I’m late lol but merry christmas & & ’ happy too & ’ happy new years all that good stuff enjoy . ❗️