544 divided by 17 yields a ratio of 32. 32 is 2 to the fifth power. Therefore it will take five half-life period to decay from 544 counts per minute to 17 counts per minute. Since the half-life is given as 30 years, it will take 150 years (5 half-lives*30 years) and the goal decay rate will be achieved in the year 2135.
