Area intersection

In a $\triangle{ABC}$ take points $P$ and $Q$ in $AB$ such that $AP=PQ=QB=30$ and points $S$ and $T$ in $AC$ such that $AS=ST=TC=40$ . Intersection of triangle $\triangle{PTB}$ and $\triangle{CQS}$ has area $640$ . Find the distance from $B$ to the line $AC$ .