The range of possible amounts of cereal c in a box can be calculated by adding and subtracting the tolerance of 0.5 ounces from the advertised amount of 19.1 ounces.
So the minimum amount of cereal in the box is:
19.1 - 0.5 = 18.6 ounces
And the maximum amount of cereal in the box is:
19.1 + 0.5 = 19.6 ounces
Therefore, the range of possible amounts of cereal c in a box is between 18.6 and 19.6 ounces.