Write circle_area(r) that returns the area of a circle with radius r, rounded to 2 decimal places. Use the constant math.pi (the math module is already imported).
Examples
Input: r = 2
Output: 12.57
Input: r = 0
Output: 0.0
Constraints
0 <= r <= 10**4
Goals
- Use math.pi from the math module
- Square a number and round the result