preposition ZAI (在) be followed by time, location, range, condition, and agent:
The tickets to the concerts will go on sale at ten o'clock this morning.
I completed my undergraduate program at Hangzhou.
The citizens aged eighteen to twenty-five are eligible to enjoy the benefits of this policy.
His grades improved significantly after receiving the meticulous training from his teacher.
The way I see it, we have to report this matter to the police.