I am having a hard time figuring out what the reserve amount is.

((gain 400,000 - reserve X ) x 1/2 ) = ?

D sold capital property in the current year for net proceeds of $700,000. The property has an adjusted cost base of $300,000. B received $60,000 at the time of the sale and a note for the balance to be paid in equal annual instalments over the following eight years. What is the minimum taxable capital gain to be reported in the current year? $ 20000