The Weight of a Product Is Measured in Pounds $\bar { X }$

Multiple Choice

The weight of a product is measured in pounds.A sample of 50 units is taken from a batch.The sample yielded $\bar { X }$
= 75 lbs. ,and we know that ?² = 100 lbs.Calculate a 99 percent confidence interval for ?.

A) $[ 71.36$$\quad$$\quad$$78.64 ]$
B) $[ 74.25$$\quad$$\quad$$75.75 ]$
C) $\left[ \begin{array} { l l } 38.58 & 111.42\end{array} \right]$
D) $\left[ \begin{array} { l l } 71.71 & 78.29\end{array} \right]$