N point t = 4, so CO=4.

Point coordinates are as follows

A(0，4)，B(-2，4)，C(-4，0)，D(-2，0)

N(4， 12)

2。 The expression of the area between MN is

s = 8 +4(t-2)-(t-2)^2

3. since AO = 4 and BA=2,

So there can't be a point P between AB that makes PB=4.