Yes. Retired cost engineers and patent agents are engaged in professional activities at the same time. They need to pay attention to the arrangement of working hours and workload to ensure that the professional activities of the two professions do not conflict with each other or affect the quality and efficiency of work. According to the "Regulations on the Management of Patent Agents" and the "Regulations on the Management of Cost Engineers", both patent agents and cost engineers need to pass the national professional qualification examination and obtain the corresponding professional qualification certificate before they can practice lawfully.