Suppose the market for cigarettes can be described as follows:

Q^s= P

Q^d= 60-P

where Q^sand Q^dare, respectively, quantity supplied and quantity demanded (in appropriate units) and P denotes price (in dollars per carton of cigarettes). Suppose the government wants to discourage smoking. In an attempt to do so, it wants to tax the suppliers in a way to bring the price of a carton of cigarettes to $40. Using matrix algebra, find the per unit tax that will achieve this goal. Discuss the incidence of the tax.