In 1944, Gutenberg-Richter Law established equation:
N = 10a-M
Here a is the constant and M represents the Richter scale magnitude, while N represents number of earthquakes in one region of magnitude at least M.
Answer the following:
(a) Calculate a, assuming that there are three earthquakes of magnitude at least six per year. Give the exact (symbolic) answer.
(b) Using assumption from part (a), how many earthquakes of magnitude at least four will happen per year in that region?