JERSEY CITY, N.J. — New Jersey-based REIT Mack-Cali Corp. has sold a 203,335-square-foot office building located at 581 Main St. in the Northern New Jersey city of Woodbridge for $61 million. The property recently underwent a capital improvement program that featured a renovated lobby and a new café and conference center. A subsidiary of Plymouth Rock Group Cos. purchased the asset and will use the building as its New Jersey headquarters. Cushman & Wakefield brokered the deal. The transaction comes as part of Mack-Cali’s stated effort to divest its suburban office assets and follows the company’s $12.7 million sale of 7 Campus Drive in Morristown two weeks ago.