magnetism again?

Question

Two long straight parallel wires separated horizontally by 4.0 cm carry currents of equal magnitude but heading in opposite directions. The wires are perpendicular to the plane of this page. Point P is between the wires, 1.0 cm from wire 1 and 3.0 cm from wire 2, and the magnetic field at point P is 1.0 × 10-2 T directed downward. Calculate the current in wire 1 and its direction.

Answer 1

Use MKS

B from one wire is uI/(2πr)
u=4πE-7
so Btotal=1E-2=uI/(2π(.01)+uI/(2π(.03)

Solving for I we get I=375 A