Available-for-Sale Securities

At the beginning of 2013, Ace Company had the following portfolio of investments in available-for-sale securities (common stock):

Security	Cost	12/31/12 Fair Value
A	$21,900	$27,900
B	34,000	31,500
Totals	$55,900	$59,400

During 2013 the following transactions occurred:

May 3	Purchased C securities (common stock) for $15,600.
July 16	Sold all of the A securities for $27,900.
Dec. 31	Received dividends of $700 on the B and C securities, for which the following information was available:

Security	12/31/13 Fair Value
B	$35,700
C	17,600

I just cannot figure out one part which is .....

What is the balance in the Unrealized Holding Gain/Loss account on December 31, 2013?

Please help!