At store a, erasers are sold individually. the cost y of x erasers is represented by the equation y=0.75x. the costs of erasers at store b are shown in the graph.
Which statement is true about the extreme value of the given quadratic equation? a. the equation has a maximum value with a y-coordinate of -21. b. the equation has a maximum value with a y-coordinate of -27. c. the equation has a minimum value with a y-coordinate of -21. d. the equation has a minimum value with a y-coordinate of -27.