The number of tennis rackets sold since 2008 at a sports store can be modeled by the function n(t) = 6t + 21 and the price per tennis racket can be modeled by p(t) = t2 - 7t + 30, where t is the number of years since 2008. according to this model, what is the total amount of revenue generated by the store's tennis racket sales in 2011?