The following functions all have domain \(\{1,2,3,4\}\) and codomain \(\{1,2,3,4,5\}\text{.}\) For each, determine whether it is (only) injective, (only) surjective, bijective, or neither injective nor surjective.

1. \(f = \twoline{1 \amp 2 \amp 3 \amp 4}{1 \amp 2 \amp 5 \amp 4}\text{.}\)

   • Injective

   • Surjective

   • Bijective

   • Neither

2. \(f = \twoline{1 \amp 2 \amp 3 \amp 4}{1 \amp 2 \amp 3 \amp 2}\text{.}\)

   • Injective

   • Surjective

   • Bijective

   • Neither

3. \(f(x)\) gives the number of letters in the English word for the number \(x\text{.}\) For example, \(f(1) = 3\) since “one” contains three letters.

   • Injective

   • Surjective

   • Bijective

   • Neither