The functions S(t) = 1.0841t + 17.392 models the amount of money, S, in billions of dollars, the United States government spent on science, space, and technology for the time period 1999-2009, where t is the number of years since 1999.
a. Write the constraints for the variable t using set-builder notation.

b. Determine the value of S(7)

c. Interpret the value of S(7) in context

d. Name the key feature that is found when solving S(t) = 0. Then, label the key feature on the graph of S(t) = 1.084t + 17.392.

e. determine if the value for S(t) = 0 is reasonable for the context. Explain why or why not.