Why am I wrong? This contour is buggin me

[flyingpig]

Homework Statement

[PLAIN]http://img88.imageshack.us/img88/4160/unledmbh.png

So my revenue function is R(d,c)

At R(100, 100) = 2000

At R(50,300) = 4000

Now R(d,c) was given (got cut off in the picture) to be linear

So I believe

R(100,100) = 100d + 100c = 2000
R(50, 300) = 50d + 300c = 4000

I got two equations, two unknowns.

Solving I get

d = 8 and c = 12

Now the answer has the answers swapped, i.e. c = 8, d = 12

 

[flyingpig]

never mind, I was the one who took R(d,c) instead of R(c,d)