Current Attempt in Progress Which of the following 3 x 3 matrices are in row-echelon form? Note: Mark all of your choices. 010 0 0 1 0 0 3 0 0 1 -1 0 O O a 0 0 -OOO W - O O O 0 0 0 O 0 0 0 0 O O O -5 un 0 O OCurrent Attempt in Progress Solve the following linear system by Gaussian elimination. X1 + 2x2+ 4x3 = 4 -x1 - 3x2 + 5x3 = 5 2 x1 - 5x2 + 6*3= 6 X1 = XO = X3 eTextbook and Media Save for LaterSolve the following linear system by Gauss elimination. -2b + 4c = 8 4a + 8b - 8c = -16 12a + 22b-19c = -39 If the system is inconsistent, type "NA" in the solution box. a = b = C =