Y = 20+2 (x-1) (1≤ x ≤ 6) Note: X should be equal to 6, so that Y will not be equal to 30 until the sixth week.

(2)y-Z=30+ 1/8(X-8) square-12= 1/8(X-8) square+18 (6

Y-z = 20+2 (x-1)+1/8 (x-8) square-12= 1/8X square+14 (1≤

In the range of (1≤X≤6), when X=6, the maximum value of Y-X is 37/2.

In the range (6

That is, when X= 1 1, Y-Z= 153/8.

Comparing the two maximum values, it is concluded that when X= 1 1, Y-Z= 153/8 is the maximum value.