The half life of thorium – 233 is 24 days. if you have a 42.0 g sample of thorium – 24, how much will remain after 72 days?

in cartography, a contour line (often just called a "contour") joins points of equal elevation (height) above a given level, such as mean sea level. a contour map is a map illustrated with contour lines, for example a topographic map, which thus shows valleys and hills, and the steepness or gentleness of slopes.

explanation:

10 years is the answer