Which line from the story shows susan calvin’s experience in programming robots?

calvin said, “but the robots are not bowed down, they are not weary, they need no rest.”

and susan calvin at once raised her electron gun and fired, and elvex was no more.

back and forth she went, her gnarled fingers tripping over the keys.

“no,” said calvin, calmly. “nor would it have occurred to me, not to anyone