I need help with Part 2, Part 1 is given for context

Most importantly: I don't understandhow everyone gets the maximum as 0.3398 and the minimum as/2 . Why is the second derivative function used to find this? How exactly is /2relevant to the question below?

Part I: Complete the following steps:

A lifeguard is at point A of a circular pool with diameter 40 m. He must reach someone who is drowning on the exact opposite side of the pool, at position C. The lifeguard swims with a speed v = 3 m/s from point A to point B, and then runs around the pool from point B to point C at speed w = 9 m/s.

1. Find a function that measures the total amount of time it takes to reach the drowning person as a function of the swim angle, expressed in radians.
2. Find at what angle , in radians, the lifeguard should swim to reach the drowning person in the least amount of time.
3. What is the domain of the function you created in part (a)?

Part II: Based on your work in Part I, discuss the following:

1. How do you know that the function you created in Part I has a maximum and minimum value?
2. Discuss how your answers to Part I would be affected if the diameter of the pool increased.
3. For what running speed would it be faster to swim the entire time? What angle would correspond to this scenario?
4. For what angle would it take the longest to reach the drowning person?