A large grocery store chain believes that 81% of its customers use the store's "Savings Card" when they make purchases. The manager in charge of the "Savings Card" program has randomly sampled 18 customers and observed whether or not they used the card. Complete parts a through c. a. Assuming that the 81% use rate is correct, what is the probability that 15 or more people in the sample used the card? The probability is 0.5446 (Round to four decimal places as needed.) b. Repeat the calculation in part a assuming that the use rate is 71%; that it is 91%. If the use rate is 71%, the probability is 0.1881. (Round to four decimal places as needed.) If the use rate is 91%, the probability is 0.9277. (Round to four decimal places as needed.) c. Based on your calculations, if 15 people in the sample used the card, which of the three use rates do you think is most accurate? Explain. Choose the correct answer below. A. The 91% use rate is the most accurate because it is the furthest from the expected value. B. The 71% use rate is the most accurate because it is the closest to the expected value