I need help with these 3 optimization problems using calculus 1 techniques. Thank you.

(1) (A) Minimize the perimeter of rectangles with area 25 cm2. (B) Is there a maximum perimeter of rectangles with area 25 cm? (2) If they exist, find two numbers whose sum is 100 and whose product is a minimum. If such two numbers do not exist, explain why. (3) If they exist, find two numbers whose difference is 100 and whose product is a minimum. If such two numbers do not exist, explain why. The of the box