Answer:
The limit on the series resistance is R ≤ 400μΩ
Step-by-step explanation:
Considering the circuit has a series of inductance and resistance. The current current in the current in the circuit in time is
(li = initial current)
So, the initial energy stored in the inductor is

After 1 hour

Knowing it is equal to 75

This way we have,
R =
μΩ
Than, the resistance is R ≤ 400μΩ