The amount of traffic in winter in Providence depends on whether it snows or not, and it snows with probability 1/3. With no snow, the time for a taxi to drive from Brown to the airport is exponentially distributed with a mean of 15 minutes. With snow, the travel time is exponentially distributed with a mean of 25 minutes. Given that it takes you 23 minutes to reach the airport, what is the probability that it is snowing?