(()) Calculate the following: (Please answer questions a and b.)

1. Carbon-14 has a half-life of 5,730 years. The sample weighs 120 grams.

a. How many years would it take for % of the original amount of carbon-14 in the sample to decay?

b. After five half-lives, how many grams of carbon-14 would remain?

2. The half-life of Pa-234 is 6.75 hours. How much (what fraction) of a sample of this isotope remains after 20-25 hours?