A group of environmentalists have written an open letter to the Supreme Court, urging it not to direct the Center or the States to spend public money on “expensive” and “inefficient” smog towers, which will “only benefit the manufacturers and sellers”. Earlier this week, the apex court had asked the Center to take a concrete decision within 10 days on whether to install smog towers in Delhi National Capital Region to combat rising pollution. The direction had come after pollution levels in Delhi peaked to a three­ year high.“India’s leading air pollution scientists and researchers unanimously say that outdoor air purifiers are inefficient to the point of being useless,” Jyoti Pande Lavakare, co-founder of Care for Air India, a non-profit advocacy group, wrote in the letter. “We earnestly request you[the Supreme Court] please do not direct any governments, local, State or Central, to spend public money to buy expensive smog towers. These are ineffective in bringing down PM2.5 levels and may even add to pollution when the dirty filters are disposed off in our already over­ flowing landfills and burnt,” read the letter. Last year, China had set up the world’s largest air purifi­cation tower in Xi’an. Co-director, Urban Emissions. Info, and Care for Air India expert Sarath Guttikunda said that at 100% efficiency, a Xi’an ­like smog tower can purify just 0.00007% of Delhi’s air.“Delhi’s air shed is around 80 km x 80 km. If you assume Delhi is a box (like a room), atmospheric height is at least 1 km (3 km in summer). At an average wind speed of 2 m/sec, the volume of air passing through the city is more than 5 trillion cubic meters per hour. The capacity of the smog tower in Xi’an is a fraction of that 4,16,000 cubic meters per hour,” he said. The reason indoor air puri­fiers work well and outdoor air purifiers do not is that this ratio is more favorable indoors, the advocacy group said. 

Answer the following questions from the above passage-

Q1. What was in an open letter which a group of environmentalists have written to the Supreme court?

Q2. Why co-founder of Care for Air India request supreme court to not direct any government to spend public money to buy expensive smog towers ?

Q3. Where China had set up the world 's largest air purification tower ?

Q4. What is the percentage of Delhi 's air that Xi'an like smog tower can purify ?

Q5. What is the capacity of the smog tower in Xi'an?