Steven works miracles as an animal chiropractor, specialising in dogs and horses, and is the only qualified animal chiropractor in the Wagga Wagga area in New South Wales. Each chiropractic treatment costs him $70 to conduct (ie: his marginal cost is constant at $70/treatment). Below is a table of the potential prices he could charge and the corresponding quantities.
Price Quantity
($/treatment) ($/treatment)
210 3
190 4
172 6
154 10
140 12
134 13

Although Steven can exert monopoly power, he decides he will set a price of $172 per treatment (without consulting any economic concepts) Answer the following questions:
What is Steven's marginal revenue when the price is $172 per tour? Answer to the nearest whole number (with no decimal places). $_________/treatment.