To do this problem, you need to use the Pythagorean thermion I think.
Here is what I got as an answer
22.5 km
I think that would be one . A=s*s A=1*1
Domain: 
Range: 
Explanation:
The function is 
The domain of a function is the set of all input values for which the function is well defined. Generally, domain consists of all x-values of the function. Hence, the function
is defined in the interval
.
The range of a function is the set of output values obtained by substituting the value of x in the function. Hence, the function
is defined in the interval
.
The 2-point form of the equation of a line can be written as ...
... y = (y2-y1)/(x2-x1)·(x -x1) +y1
For your points, this is ...
... y = (1-5)/(3-6)·(x -6) +5
... y = (4/3)(x -6) +5
It can also be written as
... y -5 = (4/3)(x -6)
The average rate of change between two input values is the total change of the function values (output values) divided by the change in the input values.