There are 28 days in 4 weeks. what fact family would you use to find the number of days in 1week

One expression below in undefined, and the other expression has a well defined value. which expression is undefined and explain why it has no value. which expression is defined? what is the value of that expression and how do you know? what is a different expression using a trig inverse function that is also undefined?

What is the surface area of the sphere?

What is an equivalent expression to ( 14400^4 )^8