… School of Management. Prior to graduate school, Jeff spent 5 years in the Energy/Natural Resources Group in Investment Banking at Lehman Brothers in New York, Houston and London where … School of Management. Prior to graduate school, Jeff spent 5 years in the Energy/Natural Resources Group in Investment Banking at Lehman Brothers in New York, Houston and London where … School of Management. Prior to graduate school, Jeff spent 5 years in the Energy/Natural Resources Group in Investment Banking at Lehman Brothers in New York, Houston and London where …