A certain city is experiencing a terrible city-wide fire. The city decides that it needs to put its firefighters out into the streets all across the city to ensure that the fire can be put out. The city is conveniently arranged into a 100 x 100 grid of streets. Each street intersection can be identified by two integers (a, b) where 1 ≤ a ≤ 100 and 1 ≤ b ≤ 100. The city only has 1000 firefighters, so it decides to send each firefighter to a uniformly random grid location, independent of each other (i.e., multiple firefighters can end up at the same intersection). The city wants to make sure that every 30 × 30 subgrid (corresponding to grid points (a, b) with A ≤ a ≤ A + 29 and B≤ b ≤ B + 29 for valid A, B) gets more than 10 firefighters (subgrids can overlap). a) Use the Chernoff bound (in particular, the version presented in class) to compute the probability that a single subgrid gets at most 10 firefighters.