A radioactive substance has a half-life of one week. In other words, at the end of every week the level of radioactivity is half of its value at the beginning of the week. The initial level of radioactivity is 20 counts per second.

a) The function that models the radioactivity remaining at the end of each week is

So the equation should be 2000(1.193)^11. Just plug that into your calculator. The way I got 1.193 is because the percentage can be converted to decimal by moving the dot two points to the left. The formula is cost(1+percentage)^years. The Answer should be about 13933.97.