Suppose parametric equations for the line segment between $(8,-2)$ and $(4,1)$ have the form:

$x(t)=a+bt$

$y(t)=c+dt$

If the parametric curve starts at $(8,-2)$ when $t=0$ and ends at $(4,1)$ at $t=1,$ then find $a,b,c,$ and $d.$

$a=$

$b=$

$c=$

$d=$