Marfan Syndrome is a rare autosomal dominant condition affecting 1 in 5000 individuals, caused by a mutation in a gene called FBN1. Mapping the FBN1 gene on chromosome 15 requires genetic linkage studies to test the segregation of FBN1 gene and DNA genetic markers on different chromosomes. A DNA marker comprising of two alleles denoted as 1 and 2, is linked to FBN1. The pedigree diagram given below gives the genotype of each family member.

Which of the following options gives the correct estimate of the recombination frequency of DNA markers among offspring?