119 I have been working on solving old US Physics Team Semifinal exams with my semifinalist student. This is a scratch paper in which I was trying to figure out a solar fusion problem. Something I didn’t remember from my undergraduate education is that in addition to energy conservation, charge conservation, and momentum conservation, nuclear processes include baryon number conservation and lepton number conservation. So solving this type of problem requires remembering which particles are of which type, as well as knowing what the types of particle are. I find it a little crazy that this test for high school students involves this kind of physics, but the test is supposed to select students to compete against other students who have been picked out of their countries as the best physics students, so it has to be hard enough to winnow out the top 20 high school physicists in the country!