(c) 384 cm2.
Let AC = x. Then BD = \(\frac{3x}{4}\)
∴ OC2 + OB2 = BC2
⇒ \(\frac{x^2}{4}\) + \(\frac{9x^2}{64}\) = 202
⇒ \(\frac{25x^2}{64}\) = 400 ⇒ x2 = \(\frac{400\times64}{25}\) = 1024
⇒ x = 32 ⇒ AC = 32 cm and BD = 24 cm.
∴ Area of the rhombus = \(\frac12\) × AC × BD
= \(\frac12\) × 32 × 24 cm2 = 384 cm2.