Answer:
a) The center coordinates O is (0,0)
b) The radius C = 15
Step-by-step explanation:
The given equation of the circle is : 
Now, general form of the equation of the circle is:

where (h,k) are the center co -ordinates and r is the radius of the circle.
Comparing the general equation with the given equation, we get

So, here the center coordinates (h,k) = (0,0)
And the radius of the given circle is r = 15
Attached below is the problem that I worked out. And I checked my answer simply by plugging it in
Answer:
1600 dollars
Step-by-step explanation:
Find out how much you earn a month
1 month = 4 weeks
1 month = 100 x 4 = 400 dollars
Now find out 4 months
4 months = 400 x 4 = 1600 dollars