Suppose s(t) is the total number of miles of railroad in the US built by the end of year t. Give an expression for cach of the following, using the function 8. (You don't need to find a formula.) (a)...

Extracted text: Suppose s(t) is the total number of miles of railroad in the US built by the end of year t. Give an expression for cach of the following, using the function 8. (You don't need to find a formula.) (a) The number of miles of railroad built by the end of 1885. (b) The number of miles of railroad built during 1884. (c) The average number of miles of railroad built per year during the 1890s.