A function for which each element in the codomain Y is the image of at most one element in the domain X and each element in the codomain Y is the image of at least one element in the domain.

a. One-to-one
b. One way
c. Onto
d. Bijection
e. Non of them

James wants to promote his band on the internet. site a offers website hosting for $4.95 per month with a $49.95 startup fee. site b offers website hosting for $9.95 per month with no startup fee. for how many months would james need to keep the website for site a to be a better choice than site b?