5. An art supplies store determines the number of markers it sells on day x of an ad campaign is S(x) = -x2 + 10x where 0 sx $ 7 (a) Find S'(x) using the definition of the derivative lim s( xth) -5(x) h=0 (b) Use your answer from part (a) to find the instantaneous rate of change after x = 3 days. Make sure to interpret the sign of your