The rate of change in revenue for DIRECTV from 2004 through 2013 can be modeled by dR/dt = 3.17 - 6.671/t, where R is the revenue (in billions of dollars) and t is the time (in years), with t = 4 corresponding to 2004. In 2010, the revenue for DIRECTV was $24.1 billion. (a) Find a model for the revenue of DIRECTV. (Round your constant term to two decimal places. Remember to use absolute values where appropriate.) R(t) = (b) Find the revenue of DIRECTV in 2013. (Round your answer to two decimal places.) $ billion