A survey of 21,250 households concerning telephone service gave the results shown in the table.

Landline

No Landline

Cell phone

12,474

5,844

No cell phone

2,529

403

a. Give a point estimate for the proportion of all households in which there is a cell phone but no landline.

b. Assuming the sample is sufficiently large, construct a 99.9% confidence interval for the proportion of all households in which there is a cell phone but no landline.

c. Give a point estimate for the proportion of all households in which there is no telephone service of either kind.

d. Assuming the sample is sufficiently large, construct a 99.9% confidence interval for the proportion of all households in which there is no telephone service of either kind.