URGENT D1 Completely Baffling Question!!!!!!! HELP

Hey guys, this question has me totally stumped. How would you attempt part B of this question?

First find the co-ordinates of A,B,C and D and substitute them into the equation p=x+ky.
You know that the value of P for A is < the value of P for D and so you can create and inequality and solve for one value of k.
You can create another inequality using the value of P for C is < the value of P for D, or another statement that is equally correct.

Thank you so much for your answer. But how do you know to pair up A with D and C?

Also in the model answer they piar it up like this, why?

Honestly, I paired those up as they were the first pairings to occur to me, but I don't think it matters which two you pair up as long as the statement itself is correct.
In answer to your second question, I think its just because that is the simplest way to gain two different values for k and so find the range. They paired up A and B, and C and D, as you only know for a fact that D has the largest profit and A the smallest, therefore you cannot create an inequality between B and C as you don't know the size of their profits in relation to each other.
I'm sorry if my explanation isn't very clear- I'll try and reword it.

I see so are you saying its a bit of random pairing? It doesnt actually matter how I pair the coordinates up? I could compare say A with C and D with B? as this is what they have in the M/S.