Math Help

3. The edible portion of grape clusters from a Mexican farm were measured to have a mean weight of 429.5 g and a standard deviation of 42.8 g. For selling purposes, the clusters are divided into two groups: Small - the lightest 20% Regular - the largest 80% a. What mass will divide the small and regular groups? b. If 20 000 clusters are picked, how many do you expect will be over 500 g? c. What assumption was made to answer the previous questions