A(t) =  is a function that models the amount (in grams) of radioactive stronlium-90 presen...

A(t) =  is a function that models the amount (in grams) of radioactive stronlium-90 present in a sample after t years.

a. How much strontium-90 is present initially?

---

b. What is the continuous annual decay rate of the sample?

---

c. When will only half of the sample remain? Give both the exact value and its four-decimal-place approximation.

---

d. How much of the sample will remain after 5 years? Round your answer to four decimal places.