The number of blogs (or weblogs) grew rapidly for several years. According to one report in august 2006, since early in 2004 the number of blogs doubled in size every six months or so. There were about 2 million blogs in march 2004. Let n denote the number (in millions) of blogs and d the number of doubling periods since march 2004. Use a formula to express n as an exponential function of d