Probability — practice question

Marco has four boxes, labelled $K$, $L$, $M$ and $N$. He arranges them in a single row as $K$, $L$, $M$, $N$, with $K$ on the far left. Marco also has four coloured marbles: one red, one green, one white and one yellow. He puts one marble into each box, chosen at random. Events $A$ and $B$ are defined as follows: $A$: The white marble is in box $L$ or box $M$. $B$: The red marble lies to the left of both the green marble and the yellow marble.