1) An animal skull discovered in a cave in Mexico contained 20% of the carbon 14 it originally contained. How old is the animal skull?

1) An animal skull discovered in a cave in Mexico contained 20% of the carbon 14 it originally contained. How old is the animal skull? The decay constant for carbon 14 is k = 0.00012

2) A community had a population of 3200 when it built a new city hall. Ten years after the new city hall was built, the population of the community was 5500. Assuming the same rate of exponential growth, what will be the population of the community twenty years after the new city hall was built?