A point charge Q moves on the x-axis in the positive direction with a speed of 370 m/s. A point P is on the y-axis at y = + 80 mm. The magnetic field produced at point P, as the charge moves through the origin, is equal to - 0.8 μT k^. When the charge is at x = + 40 mm, what is the magnitude of the magnetic field at point P? (μ0 = 4π × 10-7 T • m/A)

A. 0.57 μT
B. 1.1 μT
C. 0.92 μT
D. 0.74 μT