Given sheet of paper ABCD

AB = 40 cm, AD = 28 cm

⇒ CD = 40 cm, BC = 28 cm [since ABCD is rectangle]

Semicircle be represented as BMC with BC as diameter

Radius = (1/2) x BC=(1/2) x 28=14cm

Area of remaining (shaded region) = (area of rectangle) – (area of semicircle)