All but two of the following statements are correct ways to express the fact that a function f is onto. Find the two that are incorrect.
a. f is onto ⇔ every element in its co-domain is the image of some element in its domain.
b. f is onto ⇔ every element in its domain has a corresponding image in its co-domain.
c. f is onto ⇔ ∀y ∈ Y, 3x ∈ X such that f(x)= y.
d. f is onto ⇔ ∀x ∈ X, 3y ∈ Y such that f(x)= y.
e. f is onto ⇔ the range of f is the same as the co-domain of f.
