Answer: 
Step-by-step explanation:
The confidence interval for population mean is given by :-

, where
is the sample proportion, n is the sample size ,
is the critical z-value.
Given : Significance level : 
Sample size : n= 85
Critical value : 
Sample proportion: 
Now, the 99% confidence level will be :

Hence, the 99% confidence interval estimate of the true proportion of families who own at least one DVD player is 
A bird with roller blades.
This is a case of exponential growth. The appropriate equation, with the given data inserted, is P(t) = 500 ( 1+0.15)^50
or = 500 (1.15)^50
Evaluate this on your calculator.