Question 34252
{{{d = (16t^2)/(1+.06t) }}}
{{{21000 = (16t^2)/(1+.06t) }}}
{{{21000(1 + .06t) = (16t^2) }}}
{{{21000 + 1260t = 16t^2 }}}
{{{0 = 16t^2 - 1260t - 21000 }}}
{{{0 = 4t^2 - 315t - 5250 }}}
*[invoke quadratic "t", 4, -315, -5250]
(C)