Which of the following items would have the lowest density?
OA. A 12 cm3 block of aluminum with a mass of 2 grams
OB. A6 cm3 block of ice with a mass of 4 grams
OC. A 12 cm3 block of wood with a mass of 3 grams
OD. A 2 cm3 block of lead with a mass of 11 grams

Multiply the 3 dimensions, assuming it is a rectangular cuboid, to get the volume in cm³ divide mass by volume to get density in g/cm³

If the heat engine is a perfect carnot cycle engine, thenefficiency = (t2-t1)/t2   where t1=temperature of cold reservoir ( ° k) = 135            t2=temperature of hot reservoir ( ° k)   = 325thereforeefficiency = (t2-t1)/t2 = (325-135)/325 = 0.5846 = 58%  note: this is the theoretical maximum efficiency of a perfect heat engine.   real-life engines do not achieve this value.

Answer(b) both involve the use of levers;