10 meters of wire is available to fence off a flower bed in the form of a circular sector. What must the radius of the circle in meters be, if we wish to have a flower bed with the greatest possible surface area?	Select:
A) 5 / 2 B) 2 √ 5 C) 5 D) 4 √ 2 E) none of these

Rationale: "area of sector , a = x / 360 * pi * r ^ 2 circumference of the sector = 10 = > x / 360 * 2 * pi * r + 2 r = 20 = > 2 a / r + 2 r = 10 or 2 a + 2 r ^ 2 = 10 r = > a = r 5 - r ^ 2 = r 5 - r ^ 2 we will now max using derivations i . e 5 - 2 r = 0 r = 5 / 2 a"
Answer: A