Question: What Indian Constitution established authority estimated the money scandal around the 2G Spectrum scam?

Context paragraphs:
Sadiq Batcha: Sadiq Batcha (c. 1963 – 16 March 2011) was the Managing Director of real estate company Green House Promoters Private Limited.  Sadiq allegedly committed suicide under suspicious circumstances related to the 2G spectrum scam in India.

Shahid Balwa: Shahid Usman Balwa (born 1974) is an entrepreneur based in Mumbai, Maharashtra, India.  He is one of the promoters of Mumbai-based DB Group.  Arrested in 2011, he is currently out on bail for his alleged role in 2G spectrum scam.

Niira Radia: Niira Radia is a former corporate lobbyist and influence peddler whose taped telephone conversations implicated her influence in the allocation of key ministries in the Government of India in 2009.  Discussion of the tapes resulted in the "Radia tapes controversy", which was a media event that led to the uncovering of the 2G spectrum scam involving former telecommunications minister A Raja.  These events led to Raja's resignation and Radia's departure from corporate lobbying.

Monica (film): Monica is a 2011 Bollywood movie with Divya Dutta, Ashutosh Rana and Rajit Kapur in the lead roles and produced by ghazal singer Anup Jalota and Kush Bhargava.  It is directed by Sushen Bhatnagar and is inspired from real life incidents such as the Shivani Bhatnagar murder case and the 2G spectrum scam.

Videocon Telecom: Videocon Telecommunications Limited, formerly Videocon Mobile Services, was an Indian cellular service provider that offered GSM mobile services in India under the brand name Videocon.  The company was a subsidiary of the Videocon Group, and was headquartered at Gurgaon, Haryana.  Videocon launched its services on 7 April 2010 in Mumbai.  At its peak, Videocon held licences to provide mobile services in 18 out of 22 telecom circles of India.  However, Videocon launched commercial services only in 11 out of the 18 circles it held licences in.  Following the 2G spectrum scam, the Supreme Court cancelled 122 licences issued by the Indian Government in 2008, including 21 licences belonging to Videocon.

2G spectrum scam: The 2G spectrum scandal was an Indian telecommunications scam and political scandal in which politicians and government officials under the Indian National Congress (Congress) coalition government undercharged mobile telephone companies for frequency allocation licenses, which they used to create 2G spectrum subscriptions for cell phones.  The Government chose NM Rothschild & Sons to design a first-of-its-kind e-auction mechanism in the world, a US$2.27 billion landmark deal.  The difference between the money collected and that mandated to be collected was estimated by the Comptroller and Auditor General of India at () , based on 2010 3G and BWA spectrum-auction prices.  In a chargesheet filed on 2 April 2011 by the Central Bureau of Investigation (CBI), the loss was pegged at million () .  In a 19 August 2011 reply to the CBI, the Telecom Regulatory Authority of India (TRAI) said that the government had gained over () by selling 2G spectrum.

Comptroller and Auditor General of India: The Comptroller and Auditor General (C&AG) of India is an authority, established by the Constitution under Constitution of India/Part V - Chapter V/Sub-part 7B/Article 148, which audits all receipts and expenditure of the Government of India and the state governments, including those of bodies and authorities substantially financed by the government.  The CAG is also the external auditor of Government-owned corporations and conducts supplementary audit of government companies, i.e., any non-banking/ non-insurance company in which Union Government has an equity share of at least 51 per cent or subsidiary companies of existing government companies.  The reports of the CAG are taken into consideration by the Public Accounts Committees (PACs) and Committees on Public Undertakings (COPUs), which are special committees in the Parliament of India and the state legislatures.  The CAG is also the head of the Indian Audit and Accounts Department, the affairs of which are managed by officers of Indian Audit and Accounts Service, and has over 58,000 employees across the country.

Asok Kumar Ganguly: Justice Asok Kumar Ganguly is the former Chairman of the West Bengal Human Rights Commission and a former Judge of the Supreme Court of India who delivered judgement in some high-profile cases like the 2G spectrum scam.  He has been recently indicted by a panel of the Supreme Court for sexually harassing a young law intern in a hotel room.  He was given a clean chit after the intern refused to record her statement before the police.

S Tel: S Tel Private Limited was a GSM based cellular operator in India.  It had unified access service licenses to operate in the circles of Orissa, Bihar, Himachal Pradesh, North East, Assam and Jammu & Kashmir.  It was owned jointly by C Sivasankaran (51%) and Bahrain Telecommunications (49%).  On 2 February 2012 Supreme Court of India quashed all 122 spectrum licences granted during the tenure of former communications minister A Raja.  Six licences of S Tel were cancelled, and Batelco sold its share of S Tel.  Batelco was the first foreign operator to cease operations in India following the 2G spectrum scam.  The sale was to be completed by the end of October 2012.

Gurudas Dasgupta: Gurudas Dasgupta (Bengali: গুরুদাস দাসগুপ্ত ) (born 1936) is an Indian politician and a leader of the Communist Party of India.  He became a member of the Rajya Sabha in 1985.  He was elected the General Secretary of the All India Trade Union Congress (AITUC) in 2001.  In 2004, He was elected to the 14th Lok Sabha from Panskura in West Bengal.  In 2009, He was elected to the 15th Lok Sabha from Ghatal in West Bengal.  He is a member of JPC on 2G spectrum scam and accused Prime Minister Manmohan Singh of "dereliction of duty", alleging that he (the PM) was fully aware of irregularities in dispensing of telecom licences.  He cited a note from then Cabinet Secretary, stating the value of licences of spectrum should be increased.

Supporting paragraphs: 2G spectrum scam Comptroller and Auditor General of India
Answer: Comptroller and Auditor General of India