Answer:
28.72 mA
Explanation:
The computation is shown below:-
The expression for the magnetic field at the center

Where I indicate current in the solenoid
n indicates the number of turns per unit length of the solenoid
indicates permeability of free space
Now,
The expression for the number of turns per unit length

where
n indicates the number of turns
and l indicates the length of the solenoid
now we will combine n and b to reach the value of I

So,



= 28.72 mA