Solving a problem in physics section 24 paragraph 49 el

Solving a problem in physics section 24 paragraph 49 el

48. What is the volumetric energy density of the magnetic field in the solenoid without a core having a dense monolayer winding wire diameter of 0.2 mm, if current flows through it of 0.1 A?
49. According to the problem 71 to find the energy of the magnetic field of the solenoid, if its length is 20 cm, and 4 cm in diameter.

Additional information:

Detailed solution. Decorated in Microsoft Word 2003. (Target decided to use formula editor)