$7-8.$ An asset for drilling was purchased and placed in

service by a petroleum production company. Its cost basis

is $$60,000,$ and it has an estimated MV of $$12,000$ at the

end of an estimated useful life of $14$ years. Compute the

depreciation amount in the third year and the BV at the

end of the fifth year of life by each of these methods: $(7\mathrm{.}3,$

$7\mathrm{.}4)$

a$.$ The SL method.

b$.$ The $200\%$ DB method with switchover to SL$.$

c$.$ The GDS$.$

d$.$ The ADS.