Explain the planning steps of cash vouchers with microeconomic principles as follows:

1. The purpose of issuing cash vouchers is to promote sales and increase profits. This involves the relationship between supply and demand. Merchants can stimulate consumer demand and increase sales by issuing vouchers. At the same time, merchants should also arrange the number and validity period of vouchers reasonably to avoid inventory backlog and loss.

2. Merchants also need to consider the price elasticity of vouchers. If the incentives of vouchers are too small, consumers may not be attracted. If the preferential power is too large, the profits of the merchants will be greatly affected. Therefore, merchants need to determine the price of vouchers according to market conditions and competitors' strategies.

3. Merchants need to maximize benefits through revenue management. Revenue management is a way for merchants to seek a balance between selling price and sales volume, and can maximize revenue by adjusting prices and promoting strategies. For example, merchants can issue vouchers in the off-season or during marketing activities to attract more consumers to spend and increase sales.