A hot-wire anemometer is used to determine the boundary layer velocity profile in the air flow over a scale model of an automobile. The hot wire is held in a traversing mechanism that moves the wire in a direction normal to the surface of the model. The hot-wire is operated at constant temperature. The boundary layer thickness is to be defined as the distance from the model surface at which the velocity is 90% of the free-stream velocity. If the probe current is I0 when the hot-wire is held in the free-stream velocity, , what current will indicate the edge of the boundary layer? Neglect radiation heat transfer from the hot-wire and conduction from the ends of the wire.