"ind = [('California', 2000), ('California', 2010),
('New York', 2000), ('New York', 2010),
('Texas', 2000), ('Texas', 2010)]
pop = [33871648, 37253956,
18976457, 19378102,
20851820, 25145561]
a) How to create a multi-index object out of 'ind'?
b) How to create a multi-index series out of a multi-index and 'pop'?
c) How to turn it into a DataFrame?
