Suppose parametric equations for the line segment between $(5,5)$ and $(2,1)$ have the form:

$x(t)=abt$

$y(t)=cdt$

If the parametric, curve starts at $(5,5)$ when $t=0$ and ends at $(2,1)$ at $t=1,$ then find $a,b,c,$ and $d.$

$a=$

$b=$

$c=$

$d=$