Use gaussian elimination to find a row echelon form (not reduced row echelon form) of the augmented matrix for the following system, and then use it to determine for which value of a the following system has infinitely many solutions.

x - 2y + 6z = 1
x + 4y + z = -11
2x - 3y + az = 0

Hassan bought a package of tofu. the temperature of the tofu was 14° celsius when hassan put the package into the freezer. he left the tofu in the freezer until it reached –19° celsius. which expressions explain how to find the change in temperature, in degrees celsius, of the package of tofu? select three that apply.