For each function below give the inverse function, if it exists, else say why it has no inverse.

a) f(0)=1, f(1)=2, f(2)=3, f(3)=4, f(4)=5, f(5)=6

b) f(0)=1, f(1)=2, f(2)=3, f(3)=3, f(4)=6, f(5)=7

**Subject Mathematics Discrete Math**