Suppose the Eight-Puzzle Was Extended to a Four-By-Four Tray Containing $\begin{array} { r r r r } 1 & 2 & 3 & 4 \\5 & 6 & 7 & 8 \\9 & 10 & 11 & 12 \\13 & 14 & 15 &\end{array}$

Suppose the eight-puzzle was extended to a four-by-four tray containing 11 tiles with the solved puzzle appearing as below.
$\begin{array} { r r r r } 1 & 2 & 3 & 4 \\5 & 6 & 7 & 8 \\9 & 10 & 11 & 12 \\13 & 14 & 15 &\end{array}$
What problem would occur if our heuristic search (using the-number-of-tiles-out-of-place)was applied to solve the puzzle start from the configuration below? How could that problem be overcome?
$\begin{array} { r r r r } 1 & 11 & 15 & 12 \\5 & 6 & 7 & 8 \\9 & 10 & 2 & 3 \\13 & 14 & & 4\end{array}$