The solution of the problem 2.66 кр 2 from the problem

Task 2.66
The circuit consists of a solenoid and a current source. A solenoid without a core 15 cm long and 4 cm in diameter
It has a dense winding of two layers of copper wire with a diameter of 0.2 mm. A 1 A current flows through the solenoid.
Determine the EMF of self-induction in the solenoid at that time after it is disconnected from the source
Current, when the current was reduced by half. Resistance of the current source and supply wires
Neglected.