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6. Use the table below for z = f(x, y) to estimate the directional derivative of f in the direction v at the point P. X 0 1 2 3 4 0 65 62 59 59 60 1 62 62 63 64 64 2 65 68 69 68 68 3 62 59 58 58 60 4 65 67 69 71 73 a. At the point P (2, 2), in the direction of v = (2,0), the directional derivative is approximately b. At the point P (2, 2), in the direction of v = (3,-4), the directional derivative is approximately