Find the volume of the solid whose base is bounded in the xy plane by the graphs f(x)= and g(x)=x/3 - 1/3, and whose cross sections taken perpendicular to the y axis are isosceles right triangles with one leg of the right triangle in the xy plane

Over the course of the school year, you keep track of how much snow falls on a given day and whether it was a snow day. your data indicates that of twenty-one days with less than three inches of snow, five were snow days, while of the eight days with more than three inches of snow, six were snow days. if all you know about a day is that it is snowing, what is the probability that it will be a snow day?