As shown in the figure, it is known that the straight line y=-x+5 intersects the Y axis and the X axis at points A and B respectively, and the parabola y=-x? +bx+c passes through point a and point b, the parabola symmetry axis and straight line y=-x+5 intersect with d, and point c is the vertex of parabola.

(1) Find the coordinates of points A and B, and find the parabolic analytical formula;

(2) If point P moves from point B to point O along the X axis at a speed of 1 unit/second. The parallel line passing through point P and the parabola axis of symmetry intersects with straight line AB at point M, and intersects with parabola at point M..

① Let the movement time of point P be t, and if the circle with the diameter of MN is tangent to the Y axis during the movement of point P, try to find the t value at this time;

② Is there such a t value as CN=DM? If yes, find the value of t; If not, please explain why.

/f？ ct=335675392。 ampbaiduPostBrowser & ampsc = 1 17 1 1498847。 z= 103 1024 135。 pn = 0 & amprn = 30 & amplm = 0 & ampRS 16 = 0 & amp； word = % B3 % F5 % D6 % D0 % CA % FD % d 1% A7 # 1 17 1 1 1498847