when hits the shore on the opposite side of the river at point x, it divides the 8000 m perpendicular distance to parts a & b: (a+b=8000)

(c) makes a triangle with the 200 m river width and portion (a) of the remainder of the 8000 m minus the part of the pipe along the shore to the town:

(square of 200 + square of a= square of c)

river width (200 m) and the downstream distance of (8000 m) are perpendicular and make a traingle. Find the third wing(direct line between the refinery and the town) by adding the squares of 200 and 8000 m and taking the square root of the total= 10000 for example.

by finding this number, you have a new triangle equation between the 10000 (found above), b & c …but b & C are not perpendicular, so use the triangle formula to make the third equation (there is a formula…using the angle between the two wings):

(square of b)+ (square of c) + (2bc x cosinus of the angle between b &c) = suare of the 10000 found above.

Now you have to find a,b & c and have three equations.

Total cost is: (c x100) + (b x 75).