The extract of a plant native to Taiwan has been tested as a possible treatment for Leukemia. One of the chemical compounds produced from the plant was analyzed for a particular collagen. The collagen amount was found to be normally distributed with a mean of $64$ and standard deviation of $7.9$ grams per mililiter.

(a) What is the probability that the amount of collagen is greater than $60$ grams per mililiter?

answer:

(b) What is the probability that the amount of collagen is less than $86$ grams per mililiter?

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(c) What percentage of compounds formed from the extract of this plant fall within $3$ standard deviations of the mean?

answer: %