Audrey charges a flat fee of $4 for each delivery plus a certain amount, in dollars per mile, for each mile she drives. For a distance of 30 miles, Curtis and Audrey charge the same amount. How much does Audrey charge, in dollars per mile? Show or explain all your work

The position of a moving particle is given by the position function: f(t)=-9t-t^2-0.2t^3+0.1t^4 0 a. at what time does the particle reverse direction? b. when is the displacement positive? (round one decimal place and answer in interval notation) c. when is the displacement negative? (round one decimal place and answer in interval notation) d. when is the particle’s acceleration positive? (round one decimal place and answer in interval notation) e. when is the particle’s acceleration negative? (round one decimal place and answer in interval notation)