A 25.0 gram piece of charcoal is found in some ruins of an ancient city. The sample shows a 14C activity, R, of 250 decays/min. How long (in years) has the tree this charcoal came from been dead?
I think I have the use the equation: R=lamda*No*e^(-lamda*t) but I am not sure how I can use the 25 grams of charcoal in this equation. I have already converted 250 decays/min. into decays/year.