Find the largest positive value attained by the function
f(x)=8x−x2−14x−x2−48,xa real number<spanclass=′latex−bold′>(A)</span>7−1<spanclass=′latex−bold′>(B)</span>3<spanclass=′latex−bold′>(C)</span>23<spanclass=′latex−bold′>(D)</span>4<spanclass=′latex−bold′>(E)</span>55−5