The aortic pressure-diameter relation in a particular patient who underwent cardiac catheterization can be modeled by the polynomial D(p) = 0.000002p³ - 0.0008p² + 0.1141p + 16.683, 55 ≤ p ≤ 130, where D(p) is the aortic diameter (in millimeters) and p is the aortic pressure (in mm Hg). Determine where this function is increasing and where it is decreasing within the interval given above.