A car made a 60-mile trip at an average speed of 20 mph. On the return trip, the car's average speed was 30mph. What was the average speed of the car for the entire two-way trip? A) 30 mph
B) 26.5 mph
C) 26 mph
d) 24 mph

Twelve different video games showing substance use were observed and the duration times of game play (in seconds) are listed below. the design of the study justifies the assumption that the sample can be treated as a simple random sample. use the data to construct a 99% confidence interval estimate of μ, the mean duration of game play. 4028 4316 4816 4650 4036 5010 4833 4331 4307