closing value will be based on the lower of cost or net realisable value.

closing bal = (total amount of debit side of investment - amount of credit side except closing balance) / (no. of shares in debit side- no. of shares in credit side except closing)

and then multiplied the value by the closing shares. and it is the cost of the closing balance.

it should be less than market value.... 

lower of market price or cost.!

calculation of closing balance should be based on average basis.