I'm in pre-calculus and I'm completely clueless with these 2 problems.

1) The radioactive isotope of carbon-14c has a half life of 5730 years.

A) What is the decay constant of carbon-14c

B) If we start with a sample of 1000 carbon14 nuclei, how many will be left in 22,290 years time.

2) A Piece of charcoal of mass 25g is found in the ruins of an ancient city. The sample shows a carbon-14 activity or R(t)= 4.167 decays/second.

A) Convert the decay constant of carbon-14c from (1)(a) in terms of seconds instead of years.

B) Find the number f remaining atoms of N(t) using the constant you found in (a)

C) Suppose that the initial number of carbon-14c nuclei before decay is 1.63x10^12. What was the initial rate of decay ( or R initial)

D) How long has the tree that this charcoal came from been dead?

Okay so I'm given these equations

N(t)=Ninitial*e^-ct

R(t)=Rinitial*e^-ct

http://i40.tinypic.com/124hfdl.jpg