Hi, I am having trouble with finding probabilities.

In a game of musical chairs. A, B, and C each take one of three available chairs. Poor forlorn D comes late to nd all the chairs taken but is offered a lifeline: with probability 3, one of A, B, or C is selected at random and banished, and D is offered the open seat; with probability 4;, D is told there are no seats available. Evaluate the probability of the event that A keeps her seat when the dust has settled