I am just not catching on? Please help me work these out

Question 16 (1 point) (LO13] A random sample of 21 mobile phone screen repairs was found to have a mean repair cost of $147 with a sample standard deviation of $20. If the values are normally distributed, construct a 95% confidence interval estimate for the average repair cost of all mobile phones. 141 Amp:1562 1415 158.5 Question 17 (1 point) (L(13) Twenty five randomly selected local university students had a mean SAT acore of 10/5 points. Assume that the population standard deviation is a "5. Construct a 90% confidence interval estimate for the average SAI soon for all local university students assuming that the scores are normally distributed 1144 4. 1206 1136 1212 1 168 1182 1136 1214 Question 18 (1 point) (LO14) We want to create a 95% confidence interval estimate of the proportion of conwimers who prefer water to soda. If a previous study showed that 84% of consumers prefer water to soda, find the minimum sample sice needed for the estimate to be within 4% of the actual population proportion. O s54 Question 19 (1 point) (LC1 4) What in the minimum sample sire necessary to estimain the proportion of students who plan to take Statistics while enrolled at a particular college?' The estimated proportion should be within 3% of the population proportion ata 95% confidence level 124 125 O 1068 Question 20 (1 point) (LO14) A statistician wants to create a 90% confidence interval estimate of the mean length of flight timex from Miami International Airport to Logan Airport in Hoston to within a minutes of the true population mean. Assuming the population standard davistion is 21 minutes, what is the minimum sample sire necessary? O 20 On1 O 14