The half life for the radioactive decay of potassium- to argon- is years. Suppose nuclear chemical analysis shows that there is of argon- for every of potassium- in a certain sample of rock. Calculate the age of the rock.

This is a 2017 topographic map of puerto rico in the united states, and i'm sorry that people there have suffered such a disaster. i want to ask, what do the yellow dots and areas represent on this graph? and the blue area and the little blue circle, and the little blue sign that looks like a signal tower, what do they stand for?