Let f(x, y) = 9 – x² + xy – 5y2.(a) Find f.(1, 4) and f,(1, 4).fx(1, 4)f,(1, 4) =(b) Interpret the numbers in part (a) as slopes.f,(1, 4) is the slope of the tangent line to the curve of intersection of the surface z = 9 - x² + xy – 5y2 and the plane y= 4 at the point (1, 4, –68). f,(1, 4) is the slope of thetangent line to the curve of intersection of the surface z = 9 – x² + xy – 5y and the plane x = 1 at the point (1, 4, -68).O f,(1, 4) is the slope of the tangent line to the curve of intersection of the surface z = 9 – x + xy – 5y and the plane y = 1 at the point (1, 4, –68). f (1, 4) is the slope of thetangent line to the curve of intersection of the surface z =9 - x2 + xy - 5y2 and the plane x = 1 at the point (1, 4, -68).O f,(1, 4) is the slope of the tangent line to the curve of intersection of the surface z =9 – x2 + xy – 5y2 and the plane y = 0 at the point (1, 4, –-68). f(1, 4) is the slope of thetangent line to the curve of intersection of the surface z =9 – x2 + xy - 5y2 and the plane x = 1 at the point (1, 4, -68).O f,(1, 4) is the slope of the tangent line to the curve of intersection of the surface z =9x2 + xy – 5y2 and the plane y = 4 at the point (1, 4, 0). f(1, 4) is the slope of thetangent line to the curve of intersection of the surface z =9 – x2 + xy - 5y2 and the plane x = 1 at the point (1, 4, 0).(c) Interpret the numbers in part (a) as rates of change.O f,(1, 4) is the rate of change of f(x, y) with respect to x with y held fixed with a value of 4. f,(1, 4) is the rate of change of f(x, y) with respect to y with x held fixed with a valueof 0.O f,(1, 4) is the rate of change of f(x, y) with respect to x with y held fixed with a value of 4. f,(1, 4) is the rate of change of f(x, y) with respect to y with x held fixed with avalue of 1.O f,(1, 4) is the rate of change of f(x, y) with respect to x with y held fixed with a value of 1. f,(1, 4) is the rate of change of f(x, y) with respect to y with x held fixed with a valueof 4.O f,(1, 4) is the rate of change of f(x, y) with respect to x with y held fixed with a value of -39. f,(1, 4) is the rate of change of f(x, y) with respect to y with x held fixed with avalue of 2.

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(a) Find f,(1, 4) and f,(1, 4). ,(1, 4) = (1, 4) =