Check all true statements regarding PACs.

		PACs protect investors against extension risk
		PACs don't protect investors against contraction risk
		Within a PAC band, a PAC companion tranche's cashflows are more volatile than the PAC tranche's cashflows
		PACs offer the investor a fixed principal payment schedule if prepayment assumptions are met
		Only one PSA factor prepayment assumption threshold is used when de fining a PACs cashflows