A sample of 140 Vopstra customers have had their annual phone charge recorded for the previous calendar year. The data were used to calculate a 92% confidence interval for the mean annual phone charge of all Vopstra customers. The confidence interval was calculated as $470 + $65. According to this confidence interval, it is most reasonable to conclude that:a. you are 92% confident the interval between $405 and $535 contains the mean phone charge of all Vopstra customers b. you are 92% confident the mean phone charge of all Vopstra customers is approximately $470 c. you are 92% confident the mean phone charge of all mobile phone customers is approximately $470 d. you are 92% confident the interval between $405 and $535 contains the mean phone charge of all mobile phone customers