10. Due to employee safety negligence at a nuclear waste facility, 2000 tons of a radioactive element is spilled into the nearby pond. The half-life of the radioactive element is 36 days. In order to be declared safe for swimming, based on its size and the amount of water, there must be less than 100 tons of the material found in the pond. How long, to the nearest day, until it is safe to swim again? (5 marks) 11. 12. 13. 14. How many more times intense, to two decimal places, was the 2011 earthquake in Japan that measured 9.0 on the Richter scale than the 1905 earthquake in San Francisco that measured 8.1 on the Richter scale? (4 marks) Led Zeppelin once played a concert which exerted sounds of 10 000 times the intensity of a sound that can just be heard. What is the loudness in decibels? (2 marks) Is it possible to determine a real solution for the expression below? Explain your reasoning. (1 mark) log2(-8) Given that log2a + log2 b = 3, calculate all the possible integer values of a if b is also an integer value. Explain your reasoning. (4 marks)