The document describes a magnetic circuit with materials having permeabilities of μ, 2μ, and 4μ. It calculates the magnetomotive force (FMM) required to produce a flux Φ through the circuit. It first finds the equivalent electrical circuit by calculating the reluctance R of each section using the formula R=l/μA. It then finds the total reluctance Req and uses this in Hopkinson's law to calculate FMM=Φ*Req. Finally, it is given another magnetic circuit and calculates its total reluctance and net flux using the same process.