Physics induction question?

Question

when the 20.0 A curren through an inductor is turned off in 1.50 ms, an 800 V emf is induced, opposing the change. What is the value of the self inductance?

Answer 1

The induced emf 'E' = -L di/dt

Solving for L:

L = -E/ (di/dt)

L = -800 volts / (-20/0.0015) = 0.06 henry = 60 mH