Briefly explain why the Revenue Recognition standard does not allow the recognition of revenue in the following situation: Recently, Maria decided to invest in the manufacture of a device to relieve back pain that she designed and for which she obtained a patent. Several distributors agreed to purchase part of their inventory from Maria to resell to their customers, but only on the condition that Maria will accept back all unsold devices by the end of the first year. Maria received a total of $ 12,500 from the distributors. This is Maria's first experience in this industry and she has no idea how many units will be sold and how many will be returned to her.