Year Population 1850 23,191,876
1860 31,442,321
1870 38,558,371
1880 50,189,209
1890 62,979,766
1900 76,212,168
a. Find BOTH a linear regression equation and a quadratic regression equation for the data set.
Write the models in proper form.

Gravel is being dumped from a conveyor belt at a rate of 25 ft3/min, and its coarseness is such that it forms a pile in the shape of a cone whose base diameter and height are always equal. how fast is the height of the pile increasing when the pile is 14 ft high? (round your answer to two decimal places.) ft/min