For each real number k, define fk(x)=x3−3x+k for x in the closed interval [0,2].
a. Compute fk(0) and fk(2) in terms of k. Simplify your expressions.
b. Find all real values of k for which there exists at least one number c in [0,2] satisfying fk(c)=1. Provide a complete derivation of the required set of k-values.
c. For the specific choice k=5, verify whether a number c in [0,2] with fk(c)=1 must exist. Fully justify your reasoning without explicitly solving for c.