\fThe approximate rate of change in the number (in billions) of monthly text messages is given by the equation f'(t) = 7.1t 16.3 where t represents the number of years since 2000. In 2004 (t = 4) there were approximately 9.4 billion monthly text messages. Complete parts a. and b. below. E> a. Find the function that gives the total number (in billions) of monthly text messages in yeart. f(t) = D b. According to this function, how many monthly text messages were there in 2009? D billion