B | finexB.nb 15. Write the following logarithmic expression in simplest form as a single logarithm whose coefficient is 1. 1082 (x - 1) + 31082 y - log2 3 - 21082 Z 16. The half-life of Calcium-47 is 113 hours. a) Use the exponential model A = Ao ek' to model this data. Round k to 5 decimal places. b) How long will it take for a sample of this substance to decay to 18% of its original amount? Round to the nearest number of hours