A function has continuous second partial derivatives on an open region containing the critical point (3,

A function ƒ has
continuous second partial derivatives on an open region
containing the critical point (3, 7). The function has a minimum
at (3, 7), and d > 0 for the Second Partials Test. Determine the
interval forƒ_xy(3, 7) when ƒ_xx(3, 7) = 2 and ƒ_yy(3, 7) = 8.