A farmer finds that if she plants \( 85 \) trees per acre, each tree will yield \( 65 \) bushels of fruit. She estimates that for each additional tree planted per acre, the yield of each tree will decrease by \( 4 \) bushels. How many trees should she plant per acre to maximize her harvest? Give your answer rounded to the nearest whole number.
A linear function that models data is described below. Find the slope of the model. Then describe what this means in terms of the rate of change of the dependent variable per unit change in the independent variable. The linear function \( f ( x ) = - 0.41 x + 28.6 \) models the percentage of adults in a country who smoked cigarettes, \( f ( x ) \) , \( x \) years after \( 1997 \) .
The slope is \( \square \) . (Type an integer or a decimal.)