Answer:
The journal entries are as follows:
(a) Oil and gas properties A/c Dr. $6,600,000
To cash $6,600,000
(To record purchase)
(b)
Oil and gas properties A/c($570,000 + $450,000) Dr. $1,020,000
To cash $1,020,000
(To record additional testing and preparations)
(c) Depletion expense A/c Dr. $548,640
To accumulated depletion $548,640
(To record Depletion)
Workings:
Depletion expense:

= $548,640