Sum of last row in a cross grid

In the $4 \times 4$ array shown below, each cell of the first three rows has either a cross (X) or a number. | 1 | X | 4 | 3 | |—|—|—|—| | X | 5 | 5 | 4 | | 3 | X | 6 | X | | | | | | The number in a cell represents the count of the immediate neighboring cells (left, right, top, bottom, diagonals) NOT having a cross (X). Given that the last row has no crosses (X), the sum of the four numbers to be filled in the last row is