JMO 1991 Problem 1

Let $P,\ Q,\ R$ be the points such that $BP: PC=CQ: QA=AR: RB=t: 1-t\ (0<t<1)$ for a triangle $ABC$. Denote $K$ by the area of the triangle with segments $AP,\ BQ,\ CR$ as side lengths and $L$ by triangle $ABC$, find $\frac{K}{L}$ in terms of $t$.