A river is flowing from east to west at a speed of $5\ m/min$ . A man on south bank of river, capable of swimming $10\ m/min$ in still water, wants to swim across the river in shortest time. He should swim
Due north
Due north-east
Due north-east with double the speed of river
None of these
Given $A =\hat{ i }+\hat{ j }+\hat{ k }$ and $B =-\hat{ i }-\hat{ j }-\hat{ k }$, then $( A - B )$ will make angle with $A$
$A =2 \hat{ i }+\hat{ j }, B =3 \hat{ j }-\hat{ k }$ and $C =6 \hat{ i }-2 \hat{ k }$ Value of $A -2 B +3 C$ would be