Excluding hydropower, U. S. power plants used renewable energy sources to generate 105 million megawatt hours of electricity in 2007. By 2012. the amount of electricity generated had increased to 219 million megawatt hours. Write a linear model that represents the number of megawatt hours generated by non-hydropower renewable energy sources as a function of the number of years since 2007. Use the model to predict the number of megawatt hours that will be generated in 2017.