A wire is coiled 750 times to form a 35 cm solenoid with an inductance of 150 mH. When a current I passes through the solenoid, it produces a magnetic field inside the inductor. When the solenoid is suddenly disconnected from the voltage and connected to a resistor R, the strength of the magnetic field decreases by a factor of 4 in 250 μs. Calculate the value of R.