A trader entered into a long forward contract on a non-dividend-paying stock six months ago. At that time, the price of the stock was $100. The risk-free interest rate has been 10% per annum with semiannual compounding since then. Today the price of the stock is $90. Then, in theory, the value of the forward contract to the investor is a

$__________ ( gain , loss ) per share.

(*Underline the correct word in the parentheses, and fill in the correct number on the underlined blank space.)