The number of new members joining MySpace each year in the period from 2004 to the middle of 2007 can be modeled by m(t) 10.5t²+14t6 in millions of members where t is the time in years since the start of 2004 and is defined on the interval 0 ≤ t ≤ 3.5. What was the average number of new members joining MySpace each year from the start of 2004 to the start of 2007?