I want to obtain a sample to estimate how much parents spend on their kids birthday parties. I believe the population standard deviation is approximately 45.1 dollars. I would like to be 98% confident...

I want to obtain a sample to estimate how much parents spend on their kids birthday parties.  I believe the population standard deviation is approximately 45.1 dollars.  I would like to be 98% confident that I estimate is within 2 dollars of average spending on the birthday parties.  How many parents do I have to sample?