Answer
$P(2 \leq X \leq 3) = 0.8583$. This implies that about 86 out of 100 samples of n = 40 have a mean time between 2 and 3 inclusive.
Work Step by Step
$z = \frac{x̅ - μ}{σ_{x̅}} = \frac{2 - 2.35}{0.305} = -1.15$
$z = \frac{x̅ - μ}{σ_{x̅}} = \frac{3 - 2.35}{0.305} = 2.13$
$P(2 \leq X \leq 3) = P(-1.15 < z < 2.13)$
P(z < 2.13) - P(z < -1.15) = 0.9834 - 0.1251 = 0.8583
