Citigroup plans to cut 40 jobs in O'Fallon, Mo., as part of a broader restructuring of its mortgage business. The company plans to cut 950 jobs in that sector, of which about 650 will come from the closure of an office in Hagerstown, Md., that specializes in servicing home loans that have gone into default. Besides O'Fallon, offices in Las Vegas and Phoenix also will lose some jobs.