Pls pls help me i have been struggling with this problem for forever

Answer this question, only if you know the answer. 30 points and brainliest!

The zoo collects $9.60 for every 24 tickets sold. how much will be collected for 400 tickets?

You are standing next to a really big circular lake. you want to measure the diameter of the lake, but you don't want to have to swim across with a measuring tape! you decide to walk around the perimeter of the lake and measure its circumference, and find that it's 400\pi\text{ m}400? m. what is the diameter dd of the lake?