Archimedes' principle for buoyant force Steps:

• The block is a cube with side length a, so volume V = a³.
• Since the top surface is at depth h below the liquid surface, the block is fully immersed (assuming h > 0 and block height a).
• Upthrust (buoyant force) equals the weight of displaced liquid: F_b = ρ V g = ρ a³ g.
• The given options do not include ρ a³ g, indicating missing or ambiguous information about immersion or dimensions.

Not enough information.

Why A is wrong, etc. not applicable due to ambiguity.

Final answer: Not enough information.