PLease help, matrices

Hi guys,
Could someone please answer this with working?

An IT technician must upgrade all the PCs in an office by adding 256 MB of RAM to each machine and replacing the CPUs with a Dual Core processor.
A supplier will provide twelve Dual Core processor chip and 2048 MB of RAM for £1200 or nine Dual Core processor chip and 2560 MB of RAM for £960.
By using Determinant, matrices (inverse matrix) and Graphical methods, find how much does the supplier charges for a single Dual Core processor chip and for a single piece of 256 MB RAM. (P1, P2, P5)


Cheers,
~Bckc

Let x be the total number of lots of "twelve Dual Core processor chip and 2048 MB of RAM" ordered and let y be the total number of lots of "nine Dual Core processor chip and 2560 MB of RAM" ordered. Then the total number of Dual Core processor chips ordered is 12x+ 9y and total RAM ordered is 2048x+ 2560y. The cost will be 1200x+ 960y. You can write that information as

where "P" is the number of processor chips, "M" is the memory in MB of RAM and C is the cost.

What must x and y be so that P= 1 and M= 0? What is C in that case?
What must x and y be so that P= 0 and M= 256? What is C in that case?