Self-inductance of an air core solenoid increases from 0.01 mH to 10 mH when an iron core is introduced in it. What is the relative magnetic permeability of iron?

Self inductance of an air core inductor increases from 0.01 mH to 10 mH when an iron core is introduced in it. What is the relative permeability of the core ?

If self induction of an air core solenoid increases from 0.04 mH to 16 mH on introducing an iron core into it, what is relative magnetic permeability of the core ?

Self-inductance of an air core inductor increases from 0.01 mH to 10 mH on introducing an iron core into it. What is the relative permeability of the core used?

If the self-inductance of an iron ore inductor increases from 0.01 m H to 10mH on introducing the iron core into it, what is the relative permeability of the core used?

The self-inductance of an air-core solenoid is 4.8 mH. If its core is replaced by iron core, then its self-inductance becomes 1.8 H. Find out the relative permeability of iron.