Element X is a radioactive isotope such that its mass decreases by 67% every year. If
 an experiment starts out with 740 grams of Element X, write a function to represent
 the mass of the sample after t years, where the daily rate of change can be found
 from a constant in the function. Round all coefficients in the function to four decimal
 places. Also, determine the percentage rate of change per day, to the nearest
 hundredth of a percent.