For a real parameter a, consider the functions f(x)=ex and ga(x)=ax+2 on the closed interval [0,2].
a. Write an explicit expression for ha(x)=f(x)−ga(x).
b. Compute ha(0) and ha(2) in terms of a. State the sign of each value when a=1, a=3, and a=5.
c. Determine all real values of a for which the equation ex=ax+2 has at least one solution x in the interval (0,2). Justify your answer thoroughly.