There are 7 streets to be named after 7 tree types. Ash, Birch, Cedar, Oak, Pine, Spruce, and Willow. A city planner randomly selects the street names from the list of 7 tree types. Compute the probability of each of the following events. Event A: The first four streets are Ash, Spruce, Oak, and Birch, without regard to order. Event B: The first street is Spruce, followed by Birch then Pine, and then Ash. Write your answers as fractions in simplest form.