I too have the same question
It's a proportion, 65/100 • 39/60. To get this you do 65/100 ( that's the percent) • 39/x. You multiple 100•39 and divide that answer by 65
The bio students can be arranged in (5 · 4 · 3 · 2 · 1) = 120 different ways.
For each of those . . .
The chem students can be arranged in (5 · 4 · 3 · 2 · 1) = 120 different ways.
For each of those . . .
The physics students can be arranged in (2 · 1) different ways.
For each of those . . .
The subjects can be arranged in (3 · 2 · 1) = 6 different ways.
The whole incredibly boring line-up of presentations
can be arranged in
(120 · 120 · 2 · 6) = 172,800 different ways .
I’m most likely wrong but I think it’s C. SO SORRY IF IM WRONG IF I AM PLZ REPORT MY ANSWER
I uhm... honestly... don’t know the answer to your question I’m just trying a to uhm.... get points...