The stock price for a certain corporation can be approximated for the years 2008 through 2015 by 2 f(x) = 6.8x²-152x+937, where x = 8 corresponds to the year 2008. During what year did a local minimum stock price occur? A local extremum occurs at a critical number of f. Because the derivative exists for every x, the only critical number(s) occur where the derivative is zero. Find the derivative of f(x). f'(x)= | A local minimum stock price occurred during the year