A power generator at a dam can send 300 megawatts to substation 1, can send 200 megawatts to substation 2, and can send 250 megawatts to substation 2. In addition, substation 2 can send 100 megawatts to substation 1 and 70 megawatts to substation 3. Substation 1 can send at most 280 megawatts to the distribution center, and substation 3 can send at most 300 megawatts to the distribution center. Draw a transportation network displaying this information.