So we combine those two hypothes hypotheses  right, we get S T equals alpha  delta  gamma  plus open brackets  open the second set of brackets  one minus delta  close brackets  open brackets, one minus gamma  close  brackets  into S T minus one  minus  open brackets, one minus delta  one minus gamma  into S T minus two  right,plus  beta, delta, gamma  into P T minus one  plus  E T  minus open brackets, one minus gamma  times E T minus one, right.