A sample of iron has a mass of 257.0 lb and a volume of 0.523 ft3. What is its specific gravity? and What are the units of specific gravity?

The giant muscle protein titin is a roughly 30,000 amino acid long filament which plays a number of important roles in muscle contraction and elasticity. The I-band region of titin, largely composed of immunoglobulin-like (Ig) domains, is believed to be responsible for the molecule's extensibility and passive elasticity. The Ig domains are observed to unfold one by one; using molecular force microscopy, the force needed to unfold a single titin domain can be measured. Single domains unfold at an applied force of 1000 pN, and extend by a length of 26 nm. Interestingly, the domains don't refold until the applied force is lowered, to about 100 pN. (a)What is the work done in unfolding a single titin domain, per molecule? (b)!What is the energy of unfolding per mole? (c) If a single folding/unfolding cycle is done on the molecule, what is the net work done on the system? If the system is kept at constant temperature, what becomes of the energy in this work?