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.

$258$

$341$

$319$

$292$

$317$

$323$

$289$

$284$

$290$

$374$

$385$

$310$