You measure the lifetime of a random sample of 64 tires of a certain brand. In a follow-up study, more tires were available for testing, so you were able to measure the lifetimes of a random sample of 100 tires rather than 64. Which of the following statements is true? (a) The margin of error for your 99% confidence interval would increase (b) The margin of error for your 99% confidence interval would decrease. (c) The margin of error for your 99% confidence interval would stay the same, because the level of confidence has not changed. (d) The value of a would decrease.