400
Ms Petke tapped the lectern with a long stick and said, "That was better, but still not perfect. We've got to practice so that two weeks from now, when the show goes on, you'll sound perfect. Absolutely perfect." She tapped the stick again.
"Now, let's try it one more time," she said. "I want those bass notes to be really bass, boys. I want those soprano notes to be crystal clear, girls. Tenors, I expect you to come through full and clear. Now you sound like a bunch of birds with sore throats!"
The student laughed, then shuffled their feet and cleared their throats. They were ready to try again.
It is likely that:
a) The students are studying birds.
b) Ms. Petke is teaching the students how to play the piano.
c) Ms. Petke is leading a singing class.
What is c) Ms. Petke is leading a singing class.