In Mendelism, linkage was not observed due to

The word 'crossing over' is given by

For the preparation of genetic maps, the recombination frequencies between genes are additive over short distances but not over long distances due to

$A$ : Morgan's cross III was conducted in Drosophila to locate genes on chromosome for white eye colour.
$R$ : The cross was done between red eyed hybrid female and white eyed male.

The recombination frequency between the genes $a\, \& \, c$ is $5 \,\% \,, b\, \& \,c$ is $15 \,\%,\, b\, \& \,d$ is $9 \%, \,a\, \& \,b$ is $20 \%$ , $c\, \& \,d$ is $24 \%$ and $a \, \& \,d$ is $29 \%$. What will be the sequence of these genes on a linear chromosome?