So 00:25 plus zero point 25 plus zero point 25 plus zero point 25 gives us a total of one. So notice that these probabilities are the probabilities of these events taking place. So either we get heads and heads or we get heads and tails or tails and heads and tails and tails. So these are the four different probabilities. Now example number one tells us use the product rule, which we basically just did by multiplying it to calculate the probability that is obtained when two of those coin slips result in two heads. So this is basically this first square.