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2.06X10^-4M

Explanation: Caffeine's molar mass is 194.2 g/mole. 10 mg is 0.010 gram, so (0.01g/194.2 g/mole) = 5.15x10^-5 moles. 250 ml = 0.250 liters.

(5.15x10^-5 moles)/(0.250 liters) = 2.06x10^-4 Molar

indicate valleys, hills, steepness and gentleness of slopes.

explanation:

contour lines on a map indicate elevation, or depth. numeric notations on contour lines refer to the level of elevation, or height about sea level.