The light went off at 9:14pm, exactly six minutes after Tobi had finally understood integration by parts.
For a moment Room 112 was completely silent, the way rooms are when everyone is deciding whether to scream. Then Emeka, from the top bunk by the window, said what all of them were thinking.
"The generator will come on. They said they bought diesel."
They had said that last week too.
Tobi felt around the reading table for his rechargeable lamp. It was the only one in the room, a green plastic thing his aunty had bought at Oshodi, and it had survived two years of hostel life. When he pressed the switch, a small, brave circle of white light appeared on the table, catching the edges of four textbooks and a half-eaten pack of biscuits.
"How long does that thing last?" asked Sadiq.
"Maybe four hours. If we're lucky."
"MTH 202 is at nine tomorrow," Sadiq said, as though any of them had forgotten.
The fourth roommate, Kelechi, had not spoken all evening. He was the one who always seemed calm, who sat in front during lectures and still somehow found time to play football. Tonight he was lying on his bed with his notes on his chest, staring at the ceiling.
"Kelechi, you've finished reading abi?" Emeka asked. "Come and teach us."
"I haven't," Kelechi said quietly. "I don't understand any of it."
Nobody said anything. Tobi had assumed, the whole semester, that Kelechi was the one who had everything under control. It was strange to hear the opposite in the dark.
Tobi looked at the lamp, then at the three shapes around him.
"Bring your chairs," he said. "Everybody. We're using one light, so we're using one table."
They dragged their plastic chairs across the floor, scraping loudly enough that someone in the next room banged on the wall. Four heads leaned into the circle of light. It smelt of biscuits and mosquito coil.
"I only just understood integration by parts," Tobi admitted. "So if I explain it badly, tell me."
He explained it badly. Emeka told him. He tried again, slower, writing on the back of an old handout. The second time, Sadiq said, "Wait, so you just choose which part to differentiate?" and suddenly they were all arguing about which part, and the arguing was the most useful thing that had happened all week.
At 10:30, Kelechi took the pen. "Let me try this one," he said, pointing to a past question. He got it wrong. He tried again and got it right, and he laughed, a short surprised laugh, the first sound he had made all night that wasn't worry.
They took turns. Whoever understood a question explained it to the others. Whoever didn't, asked. When the lamp began to dim around midnight, Emeka found a phone with 40% battery and propped it against a cup with the torch on. When that died, Sadiq produced a candle nobody knew he owned.
At some point, the generator coughed to life. The fluorescent tube flickered, blinked twice, and filled Room 112 with ugly, beautiful light. They cheered so loudly that the neighbour banged on the wall again.
And then, without anyone deciding it, they stayed at the one table, shoulders touching, the green lamp switched off between them like a retired soldier.
"Sleep by one," Tobi said. "No matter what."
"Yes, sir," said Emeka.
They slept at 1:20.
Three weeks later, the results came out on the departmental notice board. Room 112 stood in front of it together. Nobody got an A. Nobody failed either. Kelechi, who had said he understood nothing, had a B.
That evening, Tobi charged the green lamp, even though there was power. It felt like the right thing to do.