Recent studies regarding addiction to videogames in a group of people yielded a function that has the subject's age in years as the independent variable and the percentage of addiction as the dependent variable f(x) = 76x -640 -2x2

a) Between what ages did the subjects show some percentage of addiction to videogames?

b) Determine the range of possible values for the percentages of addiction

c) Between what ages are people who have a percentage of addiction higher than 70%?

d) At what age is addiction peak?