<p>I'm not sure, but this is how I look at 7.</p>
<p>If Y has a higher specific heat than X, then more energy is needed to be transfered to raise Y to the lead bath temp. Which means it should have more energy to release into the water tank, so it should raise the water temp higher, which it does.</p>
<p>I don't remember thermodynamics very well either! So, this is the only crude explanation I can think of. Sorry!</p>