Let $S$ Be the Set of All Strings in 0's and 1's

Let $S$ be the set of all strings in 0's and 1's, and define a function $g$ : $S \longrightarrow \mathbf { Z }$ as follows: for each string $s$ in $S$ ,
$g ( s ) =$ the number of 1's in $s$ minus the number of 0 's in $s .$
(a) What is $g ( 101011 ) ? g ( 00100 )$ ?
(b) Is $g$ one-to-one? Prove or give a counterexample.
(c) Is $g$ onto? Prove or give a counterexample.