a) The cost of first-class postage stamp was 7/ in 1964 and 70/ in 2010. This increase represents exponential growth. Write the function S for the cost of a stamp t years after 1964(t=0). b) What was the growth rate in the cost? c) Predict the cost of a first-class postage stamp in 2018, 2021, and 2024. d) The Forever Stamp is always valid as first-class postage on standard envelopes weighing 1 ounce or less, regardless of any subsequent increases in the first-class rate. An advertising firm spent $7000 on 10,000 first-class postage stamps in 2009. Knowing it will need 10,000 first-class stamps in each of the years 2010 -2025, it decides at the beginning of 2010 to try to save money by spending $7000 on 10,000 Forever Stamps, but also buying enough of the stamps to cover the years 2011 through 2025 . Assuming there is a postage increase in each of the years 2018,2021 , and 2024 to the cost predicted in part (c), how much money will the firm save by buying the stamps? b) The growth rate is approximately 5%. (Round to the nearest integer as needed.) c) The cost of a first-class postage stamp in 2018 is . (Use the answer from part (a) to find this answer. Round to the nearest integer as needed.) The cost of a first-class postage stamp in 2021 is . (Use the answer from part (a) to find this answer. Round to the nearest integer as needed.) The cost of a first-class postage stamp in 2024 is 141. (Use the answer from part (a) to find this answer. Round to the nearest integer as needed.) d) The firm will save $ by buying the stamps at the beginning of 2010 . (Use the answers from part (c) to find this answer.)