How do I come up with these journal entries?

James Company began the month of October with inventory of $21,000. The following inventory transactions occurred during the month: a. The company purchased merchandise on account for $31,000 on October 12, 2016. Terms of the purchase were 1/10, n/30. James uses the net method to record purchases. The merchandise was shipped f.o.b. shipping point and freight charges of $560 were paid in cash. b. On October 31, James paid for the merchandise purchased on October 12. c. During October merchandise costing $18, 900 was sold on account for 529, 200. d. It was determined that inventory on hand at the end of October cost $33, 350. Required: Assuming that the James Company uses a periodic inventory system, prepare journal entries for the above transactions including the adjusting entry at the end of October to record cost of goods sold