Answer:
z=1.96
Step-by-step explanation:
Using normal distribution table or technology, 97.5% corresponds to z=1.959964, generally denoted z=1.96, or 1.96 standard deviations above the mean.
(above value obtained from R)
The answer is 12 because the lines of the parrellel shape he’ll come across each other
1k +9 > 30
1k +9 -9 > 30 -9
1k > 21
k > 21