A farmer marks four corners of a rectangular vegetable patch on the coordinate plane by tying coloured flags. The positions of the flags are described below:
• Flag A is 4 units to the right of the y-axis and 1 unit above the x-axis.
• Flag B is 8 units to the right of the y-axis and 1 unit above the x-axis.
• Flag C is 8 units to the right of the y-axis and 6 units below the x-axis.
• Flag D is 4 units to the right of the y-axis and 6 units below the x-axis.
Answer the following questions:
(a) Write the coordinates of the four flags A,B,C and D.
(b) Show that opposite sides of ABCD are parallel to the coordinate axes.
(c) Prove that ABCD is a rectangle using only the facts established in part (b) and the equality of corresponding sides inferred from the given descriptions.
(d) If another flag E is placed exactly at the midpoint of AD, write its coordinates explaining each step of your reasoning without using any formula beyond the Class 9 syllabus.