Please help me in my subject Calculus

Thankyou so much in advance!

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1. A rectangular field of a fixed area is to be enclosed and divided into 5 lots by parallels to one of the sides. What should be the dimensions of the field to make the amount of fencing a minimum?

a. L = (4/5)W ; W = (5/4) L

b. L = 2W ; W = (1/2)L

c. L = (2/3)W ; W = (3/2)L

d. L = 3W ; W = (1/3)L

2. A square metal sheet of side 48 cm has four equal squares removed from the corners and the sides are then turned up so as to form an open box. Determine the size of the square cut so that the volume of the box is maximum.

a. 6cm x 6cm

b. 8cm x 8cm

c. 4cm x 4cm

d. 2cm x 2cm

3. A company manufactures cylindrical metal containers with open top, with a volume of 1 cubic meter. What should be the dimensions of the container in order to use the least amount of metal in their production?

a. r = 0.683 m ; h = 0.26 m

b. r = 0.683 m ; h = 0.47 m

c. r = (pi) m or 3.1416 m ; h = 0.47 m

d. r = 1.57 m ; h = 0.26 m