part b and c needed please

The half-life of cesium-137 is 30 years. Suppose we have a 180 mg sample. (a) Find the mass (in mg) that remains after t years. y(t) = -(0) 30 180-2 mg (b) How much of the sample (in mg) remains after 80 years? (Round your answer to two decimal places.) mg (c) After how many years will only 1 mg remain? (Round your answer to one decimal place.) t = yr