Answer: 196
Step-by-step explanation:
As per given , we have
Population standard deviation: 
Significance level : 
Using the z-value table , the critical z value for 98% confidence : 
Margin of error : E= 01 lb
Sample size : 

Simplify , we get

Hence, the minimum sample size required for books = 196
You use the formula Y2-Y1
--------
X2-X1
8-5 3
----- = -- = -1 X=-1
3-6 -3
Get the equation simplified. Subtract 4 by each side.
20-4= 16
and the square root of 16, is 4.
Plug it in to check.
(4)^2+4=20
16+4=20
20=20
Ultimately your final answer is X=4