During a period of years, the deer population in certain country was increasing rapidly because their number of natural predators had been decreasing. The increase in population depleted food resources of the deer and eventually caused the population to decline. For the period from 1915 to 1947, the deer population was approximated by:

D(x) = -0.15x^5 + 4.86x^4 + 13400

where x is the number of years since the beginning of 1915.

a) Find the population in 1915 and round to nearest hundred:

b) Find the deer population in 1921 and round to nearest hundred:

Use a graphing calculator to:

c) Find the maximum deer population and round to nearest hundred:

d) In what year did the deer population peak: