Stumped again!! Statistics... :(

Hi guys!

THanks for all your help guys - esp Mr F!

I am stumped on these 2 questions! Any one have any idea on how to proceed?

Assuming the standard deviation for the cost of a bathroom remodel is known to be $545. How large a sample would need to be taken to estimate the mean cost of a bathroom remodel to within $136 with 99% confidence? I got 107 as my answer.

A researcher is interested in estimating the proportion of employees who are unhappy in their current. A prior study estimates this proportion at 0.13. How large a sample would need to be taken to estimate this proportion to within 4% with 95% accuracy? i got 71 as my answer

any help would be appreciated!

Cheers

Sunny