Answer: The maximum tax the government should impose on lawn mowing without discouraging either of the party in the mutual benefit is a tax less than $10. That is form $9 to $1
A tax less than $10 is acceptable because the opportunity cost is $15 and the Price Willa can pay willingly is $25. This means that if the government should impose a tax of $9, John will be making a profit of $1 from the business, while Willa won't be discouraged because she pays what she is willing to pay.