Answer
$3954.2\lt\mu\lt4345.8$ pounds
Work Step by Step
Given $n=40, \bar X=4150, \sigma=480$, use normal distribution for $n\gt30$.
At a 99% confidence the critical z-value is $z_{\alpha/2}=2.58 $ and
the margin of error can be found as $E=2.58\times480/\sqrt {40}=195.8$
Thus, the interval of the true mean is $\bar X-E\lt\mu\lt\bar X+E$ which gives $3954.2\lt\mu\lt4345.8$ pounds
