There are 7 streets to be named after 7 tree types.
Ash, Elm, Fir, 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 street is Fir, followed by Oak and then Willow.

Event B: The first three streets are Ash, Oak, and Willow, without regard to order.

Write your answers as fractions in simplest form.