Which allele combination represents a female who is a carrier for an x-linked recessive disorder?

Afemale has two x chromosomes. if the disease is an x-linked recessive disorder, and the female does not have the disease, but is a carrier of the disease, then it will contain only one  x-linked recessive allele for the disorder. 
let the allele for x-linked recessive disorder be : xr
then the genetic combination will be
xxr

    5.5 n======    assuming that      we have      m = 0.145 kg    a = 38 m/s²therefore    5.51 n, but two significant figures.final answer: 5.5 n