Vargas smiled — a rare, tectonic event. “Then you learned correctly.”

“I’ve been trying to derive the equation of motion for a bead on a rotating wire for four hours. I got ‘t = imaginary number.’”

And in a drawer, just in case, he keeps a USB drive. For the ones who truly need a teacher at 2 a.m. If you’re looking for help with specific problems from Kletenik, I can walk you through the concepts and methods — no PDF required. Just tell me the problem statement.

Matheus stared at the blinking cursor on his laptop screen. On his desk sat a cracked coffee mug, three chewed-up pens, and a stack of scrap paper covered in failed attempts. The problem on the page read: “A particle moves along a curve according to the law…” He had been stuck for six hours.

Matheus didn’t copy it. Instead, he followed each line like a detective reading a confession. At 2 a.m., he closed the PDF and picked up his pen. He solved the bead-on-wire problem himself. Then the next. Then the next.

Luisa laughed. Then she reached into her backpack and pulled out a battered USB drive. “Here. But you didn’t get it from me.”

“Did you have help?”

“Yes, sir.”