For the cost function c = 0.4q^2 + 2.8q + 9, how fast does c change with respect to q when q = 17? Determine the percentage rate of change of c with respect to q when q = 17.
1- How fast does c change with respect to q when q = 17?
$ ------- per unit
2- The percentage rate of change of c with respect to q when q = 17 is ---------