please explain step by step! thank you!

Question \#3: Skysong Company sold $8,590 of its specialty shelving to Elkins Office Supply Co. on account. Instructions: Prepare the journal entries for the following three events (a) Skysong makes the sale. (b) Skysong grants an allowance of $638 when some of the shelving does not meet exact specifications but still could be sold by Elkins. (c) at year-end, Skysong estimates that an additional $215 in allowances will be granted to Elkins