how do i solve this? answer in key is 11 cuts.

13. A ream of paper is about 2 in thick. Imagine a ream of paper that is repeatedly cut in half and the two halves stacked one on top of the other. How many cuts have to be made before the stack of paper is taller than 318 ft., the height of Le Chateau York in Winnipeg, Manitoba? Justify your answer.