(1) Find the value of a;

(2) Find the value of a 18+323a-6.

A, B and C have 10, 10 and 8 machines respectively. Now it is decided to support these machines to 18 in D and 10 in E. It is known that the freight for transporting a machine from A to D and E is 200 yuan and 800 yuan respectively. The freight charges for transporting a machine from B to D and E are 300 yuan and 700 yuan respectively; The freight charges for transporting a machine from City C to City D and City E are 400 yuan and 500 yuan respectively.

(1) We transshipped X units from City A and City B to City D. When all 28 machines were transshipped, we found the function of total freight W (yuan) about X (units), and found the minimum and maximum value of W;

(2) Let's transfer Station X from City A to City D and Station Y from City B to City D.. When all 28 machines are dispatched, express the total freight W (yuan) with X and Y, and find the minimum and maximum value of W. 。