You're interested in dating some igneous rocks that you've found in the Canadian Shield. In order to apply radiometric dating techniques, we must first establish a parent and daughter pair of isotopes that we will analyze. Due to the abundance of Potassium-40 and its daughter element, Argon-40, we will let the lab technician know that we're interested in studying the relative amounts of those substances.

A few days later, the lab technician calls and informs you that there is a 1:3 ratio of the parent and daughter isotopes.

For this question, I want you to tell me a) what this 1:3 ratio represents in terms of time/half-life, b) how old the rock is based on this ratio (the half-life of K-40 is 1.3 billion years), and c) what is a potential source of error when using this parent and daughter isotope pair?