Mumbai, July 30 -- Shares of Vodafone Idea Ltd slumped 27% on Monday and now trade at merely Rs.6.75 apiece. When Vodafone India Ltd and Idea Cellular Ltd had announced their merger in March 2017, they had envisaged a far greater value for the stock. At that time, the merger pact included a clause that gave Idea Cellular's promoter the right to purchase shares in the merged entity from Vodafone Group Plc at Rs.130 per share....