As West Bengal Assembly elections draw closer, one thing that has caught the public eye is the coal scam. The CBI will interrogate Rujira Banerjee, wife of Abhishek Banerjee, nephew of CM Mamata Banerjee in this case. The CBI also sent a notice to Abhishek Banerjee and his sister-in-law Maneka Gambhir. Here is an explainer on why Mamata Banerjee's family is under the CBI Radar ahead of the Assembly polls