What is the formula for the net cross sectional area of the core of the transformer?

• A. cross sectional area = voltage per turn * 4.44 * frequency * magnetic field
• B. cross sectional area = voltage per turn / 4.44 * frequency * magnetic field
• C. cross sectional area = voltage per turn * 4.44 / frequency * magnetic field
• D. cross sectional area = voltage per turn * 4.44 * frequency / magnetic field