In a particular region there is a uniform current density of 18 A/m^{2} in the positive direction. What is the value of fB·ds when that line integral is calculated along the three straight-line segments from (x, y, z) coordinates (5d, 0, 0) to (5d, 3d, 0) to (0, 0, 0) to (5d, 0, 0), where d = 19 cm?