An aluminum rod 10.0cm long and a steel rod 80.0cm long are combined to form one rod with a total length of 90.0cm. The initial temperature of both rods is 15 degrees celcius. The expansion coefficient of aluminum is 2.4*10^5 and the expansion coefficient of steel is 1.2*10^5. When the combined rod is heated to 90 degrees celcius, what is the total change in length? What is the expansion coefficient of the combined rod?