<span>Johann Heinrich von Thünen, a Prussian landowner, introduced an early theory of agricultural location in Der isolierte Staat (1826) (The Isolated State). The Thünenmodel suggests that accessibility to the market (town) can create a complete system of agricultural land use</span>
(a)
We have been given an equation
. Upon taking derivative of this equation with respect to x on both the sides, we get:

(b)
In order to write the equation of tangent line, we need to find the slope of the line. We know that point (3,11) lies on the graph. Therefore, we write the slope of the tangent as:

Therefore, equation of tangent line is:

(c)
We know that slope of tangent is given as
. The tangent will be vertical when denominator of slope is zero, that is:

6 not 6- just 6 glad i can help