Inventory was purchased on credit in April and paid for in May by Lebel Lte. Lebel sold

Inventory was purchased on credit in April and paid for in May by Lebel Ltée. Lebel sold and delivered the merchandise, along with an invoice, to a customer in June. The customer paid Lebel for the merchandise in July. 

(a) In which month should Lebel record the sale as revenue and in which month should Lebel record the cost of goods sold as expense? 

(b) In which month should the customer record the purchase of inventory from Lebel?