The bell for the next class

Robyn caught up with Sandry as the bell rang.

"Come on, we can't be late." she said.

"I can't find a top!" Sandry cried, looking up from her locker, "My PE t-shirt isn't here. Can you grab yours for me?"

"You know mine wouldn't fit you." Robyn replied, gesturing first to her unfortunately rather flat chest, and then Sandry's rather more impressive one.

"It would be better than being topless, wouldn't it?"

"Only until you burst out of it, which would take you about thirty seconds. Now let's go, before they realise we're late."