The volume (in cubic feet) of a black cherry tree can be modeled by the equation

ŷ = -52.2 + 0.3x₁ + 4.5x₂

where x₁ is the tree’s height (in feet) and x₂ is the tree’s diameter (in inches).

(a) x₁ = 70, x₂ = 8.6

(b) x₁ = 65, x₂ = 11.0

(c) x₁ = 83, x₂ = 17.6

(d) x₁ = 87, x₂ = 19.6

Use the multiple regression equation to predict the y-values for the values of the independent variables.