91Ó°ÊÓ

Given,

$\mathrm{μ}=450,\mathrm{σ}=20$

USe the Formula :

$Z=\frac{X-\mathrm{μ}}{\mathrm{σ}}$

Consider,

The book's Z table can be used to compute the 5th percentile; look for the associated Z value within the table.

$$\begin{gathered} Z=\frac{X-\mathrm{μ}}{\mathrm{σ}} \\ X=\mathrm{σ}*Z+\mathrm{μ} \\ X=-1.645*20+450=417.1 \end{gathered}$$

Knowing that $Z=-1.645$

$X=418$

Therefore, the correct option is (c)

a. The minimum number of unbroken briquets the bag would have to contain for the company to avoid having to replace the bag for free is not $404$

b. The minimum number of unbroken briquets the bag would have to contain for the company to avoid having to replace the bag for free is not $411$

d. The minimum number of unbroken briquets the bag would have to contain for the company to avoid having to replace the bag for free is not $425$

e. The minimum number of unbroken briquets the bag would have to contain for the company to avoid having to replace the bag for free is not $448.$