D=kt^2
45=9k,k=5
D=5(36)=180m
20=5t^2
4=t^2
t=2seconds
Phew. There’s your answer.
Tectonically stable means that this part of the continent has not moved for billions of years. The rock formation is important understanding the history of Earth since its unmoved and untouched state can provide ideas about how the Earth looked like as seen on the layers of the rock formation.
The Mercator . tbh i googled it and thats what came up on some sites