elta Oil Company Limited a successful effort accounting company has $23$ leases in its unproved properties portfolio at $31$ December $2008.$ The lease together with the applicable impairment and acreage were summarized as follows

Average $($N$)$

Lease B$-1...........................\mathrm{.}780$

Lease B$-2...........................\mathrm{.}1000$

Lease B$-3............................\mathrm{.}200$

Other leases $(20$ in number$)....3,500$

Cost $($N$)$

$120,000$

$160,000$

$100,000$

$250,000$

Impariment $($N$)$

$24,000$

$32,000$

$20,000$

$42,000$

Delta considers leases B$-1,$ B$-2$ and B$-3$ to be individually significant. The remaining $20$ leases are considered individually insignificant. During $1998,$ the following events occurred:

$1.$ An exploratory well drilled on lease B$-1$ resulted in a dry hole

$2.$ The well drilled on lease B$-2$ was successful

$3.$ Drilled activities had not commenced on lease B$-3$ but the result of a well drilled in a nearby property was unsuccessful

$4.$ A lease with an original cost of N$50,000$ included in "other leases" was surrendered.

Experience shows that approximately $30\%$ of other leases will ultimately become productive and that the average holding period of the remaining leases is five years.

REQUIRED

$($a$)$ Prepare necessary journal entries

$($b$)$ Show the net carrying value of unproved properties at $31$ December $2008$ for other leases