1.Devise the exponential growth function that fits the given data, then answer the accompanying question. Be sure to identify the reference point (t0) and units of time. Uranium-238 (U-238) has a half-life of 4.5 billion years. Geologists find a rock containing a mixture of U-238 and lead, and determine that 79% of the original U-238 remains; the other 21% has decayed into lead. How old is the rock?

Devise the exponential growth function that ts the given data, then answer the accompanying question. Be sure to identify the reference point (t = 0) and units of time. Uranium-238 (U-238) has a half-life of4.5 billion years. Geologists nd a rock containing a mixture of U-238 and lead, and determine that 79% of the original U-238 remains; the other 21% has decayed into lead. How old is the rock? What is the reference point (t = 0)? . When the rock does not contain any more of the original amount of U-238. . When the rock contained 100% of the original amount of U-238. . The state of the rock 4.5 billions years ago. . The current state of the rock with 79% of the original amount of U-238. What are the units of time? months decades billions of years yea rs Write the exponential growth function. Use yo the initial value of y. ya) = (Type an expression. Round coefcients to three decimal places as needed.) How old is the rock? The rock is D billion years old. (Round to three decimal places as needed.) A certain drug is eliminated from the bloodstream with a half-life of 36 hours. Suppose that a patient receives an initial dose of 70 mg of the drug at midnight. a. How much of the drug is in the patient's blood at noon later that day? b. When will the drug concentration reach 25% of its initial level? a. The reference point is V If t is measured in hours, what is the exponential decay function? W) = (Type an expression. Do not round until the final answer. Then round coefficients to six decimal places as needed.) How much of the drug is in the patient's blood at noon later that day? There are approximately mg of of the drug in the patient's blood at noon later that day. (Do not round until the final answer. Then round to two decimal places as needed.) b. When will the drug concentration reach 25% of its initial level? After hours, the drug concentration will reach 25% of its initial level. (Do not round until the final answer. Then round to two decimal places as needed.) Find the area of the surface generated when the given curve is revolved about the given axis. 3 X y= E' for 05x5 10; about the x-axis The surface area is I: square units. (Type an exact answer, using a: as needed.)