t2=AC/3;
t1=AC/9;
(v1+3)*AC/9=AC;
(v2-3)*AC/9=AB-AC;
(v1+3)*AC/3=AB;
(v2+3)*AB/(v1+v2)=40;
v1+3=9;
v1=6;
(v1+3)*AC/3=(6+3)*AC/3=3AC=AB;
(v2-3)*AC/9=3AC-AC=2AC;
(v2-3)/9=2;
v2-3=18;
v2=21;
(v2+3)*AB/(v1+v2)=(21+3)AB/(21+6)=40
24/27AB=40
AB=45 км.
: v1=6; v2=21; AB=45.