A cup of coffee was made at a temperature of 90∘ and cools according to Newton's law of cooling. The room temperature is 30∘. If the temperature of the coffee 20 minutes after being made was 40∘ (a) What was the temperature of the coffee 15 minutes after being made?

answer is: naturally occurring solid, inorganic compound or element is mineral.

minerals usually have crystalline form, that means than crystal constituents (atoms, molecules or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions.

for example magnetite is a mineral of iron oxide (fe₂o₃).

calcite is a carbonate mineral and the most stable polymorph of calcium carbonate (caco₃).

dolomite is an   carbonate mineral composed of calcium magnesium carbonate (camg(co₃)₂).