The half-life of cesium-137 is 30 years. Suppose we have a 60 mg sample. (a) Find the mass that remains after t years. y(t) = mg (b) How much of the sample remains after 150 years? (Round your answer to two decimal places.) y(150) = mg (c) After how long will only 1 mg remain? (Round your answer to one decimal place.) t = years