#QFMB 10 POINT how would you measure a planets surface's altitude if there was no ocean for 'sea level' or 0 to start from?

In the diagram below, ab and bc are tangent to o. what is the measure of

Afootpath is to be constructed in a park in the shape of a parallelogram. when a coordinate plane is laid over a map of the park, the vertices of the footpath are (-4,2) (8,2) (11,7) and (-1,7). what is the perimeter of this path

What is the biggest country in south america?