3. A family decides to produce children until they have n daughters, and then stop. On average, how many children will they have? Hint: write the total number of children as the sum of n appropriate random variables. (You may assume that the probability of each child being a daughter is 1/2, independent of any other children.)

4. The side length (in cm) of an equilateral triangle is uniformly distributed on [2, 5]. Find the expected value of the area of the triangle, to 3 decimal places. (Hint: if you do not remember how to compute the area of an equilateral triangle, you may look it up.)