Okay.
5.5 million square miles is 14,244,934.6 km^2
5,000 feet is 1.524 km.
Since volume is the product of all three dimensions, the total volume is 14,244,934.6 * 1.524, which is 21,709,280 km^3.
But, we need that in units of cubic centimeters, not cubic kilometers. Since 100,000 cm are in 1 meter, there are 1*10^15 cubic centimeters in a cubic meter. So, we can conclude that the volume of the ice sheet in cubic centimeters is 2.17092803*10^22, by multiplying the volume by its conversion factor.
Since the density is 0.92 grams for every cubic centimeter of ice, the total mass of the entire ice sheet is 2.0*10^22 grams, or 2.0*10^16 metric tons. This is, of course, taking significant figures into consideration within the final answer.
Dammit Woeler, you beat me to it.




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