The World Bank has sponsored a project to curb air pollution through public transport improvements and the Mexican government has started shutting down polluting factories. They have phased out diesel buses and mandated new emission controls on new cars; since 1993 all new cars must be fitted with a catalytic converter, which reduces the emissions released. Trucks must use only liquefied petroleum gas (LPG). Also construction of an underground rail system was begun in 1968 in order to help curb air pollution problems and alleviate traffic congestion. Today it has over 201 km (125 mi) of track and carries over 5 million people every day. Fees are kept low to encourage use of the system and during rush hours the crush is so great, that authorities have reserved a special carriage specifically for women. Due to these initiatives and others, the air quality in Mexico City has begun to improve, with the air becoming cleaner since 1991, when the air quality was declared to be a public health risk for 355 days of the year.[citation needed]
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): How many people ride the Mexico city subway system each day?
Ah, so.. 5 million people

The breakup of the Carolingian Empire was accompanied by invasions, migrations, and raids by external foes. The Atlantic and northern shores were harassed by the Vikings, who also raided the British Isles and settled there as well as in Iceland. In 911, the Viking chieftain Rollo (d. c. 931) received permission from the Frankish King Charles the Simple (r. 898922) to settle in what became Normandy.[Q] The eastern parts of the Frankish kingdoms, especially Germany and Italy, were under continual Magyar assault until the invader's defeat at the Battle of Lechfeld in 955. The breakup of the Abbasid dynasty meant that the Islamic world fragmented into smaller political states, some of which began expanding into Italy and Sicily, as well as over the Pyrenees into the southern parts of the Frankish kingdoms.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): In what region of modern-day France did the Vikings settle?
Ah, so.. Normandy

The book value of the company nearly doubled from $8.19 a share in 1999 to $15 a share in 2009. Revenues grew sixfold from 1999's $6 billion to almost $36 billion in 2009. Net profit margin rose from 4.2% in 1999 to 8.4% in 2009, with operating margins improving 31 percent and return on equity doubling to 6.7 percent in the same time span. Between 1999 and 2009, return on capital nearly tripled to 7 percent. Comcast reported first quarter 2012 profit increases of 30% due to increase in high-speed internet customers. In February 2014, Comcast generated 1.1 billion in revenue during the first quarter due to the Sochi Olympics,.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): What sports event caused revenues to double from 1999 to 2009?
Ah, so..
unanswerable