Applications of LU-decomposition

You're given a matrix $A$. Find such $LU$-decomposition for it that all elements of the main diagonal of matrix $L$ are equal to $1$. Write down the sum of all elements of the matrix $U$ accurate to $1$ decimal place.

$$A={\begin{pmatrix} 5 & -2 & 3 & 17\\ -7 & 8 & 13 & 5\\ -1 & 1 & 7 & -8 \\ 4 & -4 & -3 & 1\\ \end{pmatrix}}$$