A Baldwin-United unit agreed to sell a business.

The Baldwin-United subsidiary, Ambac Indemnity, said its MGIC Investment subsidiary signed a definitive agreement with a company formed by Ambac’s management to acquire Ambac’s municipal bond insurance business. The transaction is expected to be completed by March 31. No changes in operations are expected. The new business will bear the Ambac name and will be based in Wisconsin. This is the last major step, sought by a special masters commission set up by Arkansas and Indiana courts, toward separating the MGIC companies from the financial difficulties of Baldwin-United, which acquired MGIC in 1982.