Comcast, the country’s largest cable company, announced Monday that it will divest 3.9 million subscribers to regional cable operator Charter as part of a plan to ease regulatory concerns over its proposal to acquire Time Warner Cable. The planned divestures, which have been valued at around $20 billion, call for Comcast to sell 1.4 million subscribers to Charter directly, and to create a spinoff corporation to serve 2.5 million customers that will also be owned in part by Charter. The plan also calls for a swap of existing customers, with Comcast acquiring Charter subscribers in Los Angeles and Charter acquiring Comcast subscribers in the Midwest. The plan is consistent with what Comcast proposed in February when it announced plans to swallow its second biggest rival, Time Warner Cable.