An internet service provider (ISP) has experienced rapid growth in the past five years. As part of its marketing strategy, the company promises fast connections and dependable service. To achieve its objectives, the company constantly evaluates the capacity of its servers. One component of its evaluating is an analysis of the average amount of time a customer is connected and actively using the Internet daily. A random sample of 12 customer records shows the following daily usage times, in minutes. Complete parts a through d below. 274 332 289 325 305 344 301 263 287 372 361 347 316.67 minute(s) (Round to two decimal places as needed.) b. The managers of the ISP's marketing department would like to develop a 99% confidence interval estimate for the population mean daily customer usage time. Because the population standard deviation of daily customer usage time is unknown and the sample size is small, what assumption must the marketing managers make concerning the population of daily customer usage times? The sample size is at least 30. The population distribution is unknown. I The population distribution is approximately normal. The population distribution is uniformly distributed. c. Construct and interpret the 99% confidence interval estimate for the mean daily usage time for the ISP's customers. The 99% confidence interval estimate is m minute(s) minute(s). (Round to two decimal places as needed. Use ascending order.)