The radioactive element plutonium 238 (Pu-238) has a half-life of 88 years. This means that the element loses half of its mass every 88 years. A sample of Pu-238 has a mass of N grams today. How do you determine the amount of the sample remaining after 352 years (4 half-lives)?

1. according to the internal revenue service, the mean tax refund for the year 2007 was $2,708. assume the standard deviation is $650 and that the amounts refunded follow a normal probability distribution. a. what percent of the refunds are more than $3,000? b. what percent of the refunds are more than $3,000 but less than $4,000? c. what percent of the refunds are less than $2,000?