In 2019, Walmart conducted the same study on their SZ customers. The amounts those customers spent were again normally distributed. Below are 15 randomly selected amounts. 1,200 1,500 1,650 1,700 1,750 1,800 1,960 2,000 2,100 2,420 2,450 2,450 2,480 2,500 2,500

Question 11: Estimate the proportion of SZ customers in 2019 who spent less than 2,400 on the day of New Year's Eve based on the sample provided above at a 95% confidence level.

Question 12: Estimate the variance of the amounts spent by SZ customers in 2019 based on the sample provided above at a 95% confidence level.