$\backslash$table$[[\backslash$table$[[$To$],[$FrOM$]],\backslash$table$[[$Coal$],[$Valley$]],$Coaltown,$\backslash$table$[[$Coal$],[$Junction$]],$Coalsburg,Supply$],[,,50,,30,,60,,70,],[$Morgantown$,30,[$o$,5,$R$,8,,2,,35],[,,20,,80,,10,,90,],[$Youngstown$,,,40,,20,$a$,1,x,60],[,$T$,100,y,40,0,80,,30,],[$Pittsburgh$,4,,12,r^2,5,2,20,,25],[$Demand$,30,x,45,x,25,x,20,-,120]]$

If the best improvement index is $-110$ from Pittsburgh to Coaltown. What is the Filling quantity for this cell and modifying those cells on the stepping stone path?

a$.40$

b$.0$

c$.20$

d$.5$