Jawaban:

Dari perumusan hukum Pascal diperoleh

begin mathsize 14px style table attributes columnalign right center left columnspacing 0px end attributes row cell F subscript 1 over A subscript 1 end cell equals cell F subscript 2 over A subscript 2 end cell row cell fraction numerator F subscript 1 over denominator straight pi R subscript 1 squared end fraction end cell equals cell fraction numerator F subscript 2 over denominator straight pi R subscript 2 squared end fraction end cell row cell F subscript 1 over R subscript 1 squared end cell equals cell F subscript 2 over R subscript 2 squared end cell row cell fraction numerator F subscript 1 over denominator 1 space cm squared end fraction end cell equals cell fraction numerator 400 space straight N over denominator left parenthesis 20 space cm right parenthesis squared end fraction end cell row cell F subscript 1 end cell equals cell 1 space straight N end cell end table end style

Jadi, jawaban yang tepat adalah B.