Our sales during the month of April alone of legacy non-agencies, CRTs, and MSR-related assets generated over $150 million of realized gains versus March 31 marks.
We signed these agreements last night and we're happy to announce today that we have entered into an agreement with Apollo and Athene, an insurance company affiliate of Apollo, to raise $500 million in the form of a senior secured note.
But this $500 million note is only part of a holistic solution for MFA and a very strategic partnership with Apollo and Athene.
Apollo and Athene together have arranged a committed term borrowing facility with Barclays of approximately $1.65 billion that includes over $500 million for participation from Athene.
Pro forma for these facilities, approximately 60% of the Company's financing will be in the form of non-mark-to-market funding, providing shareholders with significant downside protection in the event of future market volatility.
We expect that upon closing and funding of these transactions, we'll be able to satisfy remaining margin calls, which were only $32 million as of June 12 and exit from the current forbearance agreement on or before June 26.
Apollo and Athene have also committed to purchase the lesser of 4.9% or $50 million of MFA stock in the open market over the next 12 months.
Prices of legacy non-agencies, which had not changed by more than 3 points in the last two to three years, were suddenly lower by 20 points.
CRT securities dropped as much as 20 points to 50 points and MSR-related asset prices were lower by 20 points to 30 points, all in a few days.
MFA received almost $800 million in margin calls during the weeks of March 16 and March 23 and over $600 million of these were on mortgage-backed securities.
In contrast, we received $7 million of margin calls on these portfolios during the entire week of March 2 and $37 million during the week of March 9.
And during the months of December, January, and February, we received a total of six margin calls, all related to factor changes with a total aggregate amount of $4 million.
During those same three months, we initiated 10 reverse margin calls totaling $14 million, meaning we received net $10 million more from our lenders due to price increases.
Our first quarter financial results were profoundly affected by realized losses, impairment losses, unrealized losses on loans accounted for at fair value, provisions for credit losses under the new CECL standard and valuation adjustments on assets designated and held-for-sale and resulted in a loss of $914 million or $2.02 per share.
Book value decreased to $4.34 per share at March 31 and economic book value decreased to $4.09 per share.
Page 7 of the earnings deck shows portfolio activity from December 31 to March 31 and then again from March 31 to May 31.
As you can see from the pie charts, we have sold substantially all of our mortgage-backed securities and our $6.6 billion portfolio is approximately 94% whole loans.
In rough numbers, our whole loan portfolio today is comprised of non-QM loans, $2.4 billion, loans at fair value, $1.2 billion, fix and flip loans, $850 million, purchase credit impaired or reperforming loans, $660 million, single family rental, $500 million, season performing loans, $150 million, and REO or real estate owned of $375 million.
With the committed $1.65 billion in our existing securitizations of approximately $500 million, we will have over $2 billion of such financing.
Spreads for AAA securities widened out from the 100 area, that's 100 over swaps in early March to as wide as plus 400 at the depth of the crisis, but they've been slowly grinding tighter and are now back to mid-100 levels.
One, at present we have undistributed REIT taxable income from 2019 of $0.05 per share.
Two, estimated REIT taxable income or ordinary income for the first quarter of 2020, is approximately $0.10 per share.
In order to avoid paying a 4% excise tax on this amount, we are required to declare dividends in 2020 for at least 85% of our estimated 2020 REIT taxable income.
While we cannot forecast ordinary REIT taxable income for the balance of 2020, any such income generated will be added to the $0.10 in the first quarter in determining the threshold necessary to avoid the 4% excise tax.
At June 12, our unrestricted cash was $242 million.
Book value as of May 31 -- GAAP book value is estimated to have increased by approximately 2% to 3% versus March 31.

Summary:
Apollo and Athene together have arranged a committed term borrowing facility with Barclays of approximately $1.65 billion that includes over $500 million for participation from Athene.
Apollo and Athene have also committed to purchase the lesser of 4.9% or $50 million of MFA stock in the open market over the next 12 months.
Our first quarter financial results were profoundly affected by realized losses, impairment losses, unrealized losses on loans accounted for at fair value, provisions for credit losses under the new CECL standard and valuation adjustments on assets designated and held-for-sale and resulted in a loss of $914 million or $2.02 per share.
With the committed $1.65 billion in our existing securitizations of approximately $500 million, we will have over $2 billion of such financing.