Step 1: Identify total Sundays in a leap year. A leap year has 366 days, which means 52 complete weeks + 2 extra days.
Step 2: Determine favorable cases. The extra 2 days can be: \begin{itemize} \item - (Sunday, Monday) \item - (Monday, Tuesday) \item - (Tuesday, Wednesday) \item - (Wednesday, Thursday) \item - (Thursday, Friday) \item - (Friday, Saturday) \item - (Saturday, Sunday) \end{itemize} In 2 out of 7 cases, Sunday is included.
Step 3: Compute probability. \[ P(\text{53 Sundays}) = \frac{2}{7} \]
Let the mean and variance of 7 observations 2, 4, 10, x, 12, 14, y, where x>y, be 8 and 16 respectively. Two numbers are chosen from \(\{1, 2, 3, x-4, y, 5\}\) one after another without replacement, then the probability, that the smaller number among the two chosen numbers is less than 4, is:
If the mean and the variance of the data 
are $\mu$ and 19 respectively, then the value of $\lambda + \mu$ is