(4) Suppose a (t) 2 + t + ?. If $ 1 00 invested at time 0 accumulates to $ 1 52 at time 4 and $200 invested at time 0 accumulates to $240 at time 2, find the accumulated value at time 8 of $1,600 invested at time 6. [HINT: First find the unknowns ? and ?. Then determine how much money X that you would need to deposit at time 0 in order to have an accumulation of $1,600 at time 6. The desired answer is the accumulated value of X at time 8.]