(2) First, determine the P coordinate (0, -2.5+t), PM⊥AB, and the slope product is-1. Then, solve the simultaneous equations of PM, AC, and N coordinates with known intersection points, and then use the midpoint coordinate formula to find Q. The absolute value of the ordinate of Q is QT length, and the ordinate is positive or negative, so it is between it and T.
(3) If 3)PM and AB are known, find the M coordinate of the intersection; if M and P coordinates are known, find QM with the distance formula between two points. Because QT in question (2) is discussed by segments, we must pay attention to whether the t values obtained in different intervals are uniform in this interval, and discard them if they are not uniform. Compare the slopes of the two lines, which are also parallel. The product of the slopes is-1 which is vertical, and neither of them is oblique, so it should be parallel here.