Consider a securitization pool that uses borrowed money to purchase $1 billion worth of mortgages paying 6%. To raise money to pay back the loan, the trust sells $600 million in tranche A securities that pay 3%,$300 million in tranche B securitie that pay 6%, and $100 million in tranche C securities that pay 8%. What is the interest rate spread? 1) 6.0% 2) 1.3% 3) 3.6% 4) 1.0% 5) none of the above