A matrix A is said to be in 'row echelon form' if its non-zero entries describe a flipped staircase pattern. Formally this means that: All rows of A consisting of only zeroes are at the bottom. The leading coefficient (also called the pivot) of a non-zero row of A is always strictly to the right of the leading coefficient of the row above it. Write the function is row echelon(a) that determines whether a matrix a is in row echelon form