(b) 10 cm2.
OS = OP = ON = radii of the circle = 5 cm
(OS)2 = (OK)2 + (KS)2
⇒ 25 = (OK)2 + 16
⇒ (OK)2 = 25 – 16 = 9
⇒ OK = 3 cm
LC = KB
⇒ LN + NC = KS + SB
⇒ LN + 2 = (4 + 1) cm ⇒ LN = 3 cm
Similarly, (ON)2 = (OL)2 + (LN)2 ⇒ 25
= (OL)2 + 9
⇒ (OL)2 = 16 ⇒ OL = 4 cm
∴ LK = OL – OK = (4 – 3) cm = 1 cm
Also, AB = DC = 10 cm
∴ Area of rectangle ABCD = AB × BC = 10 cm × 1 cm = 10 cm2.