The area of a square is 36 sq ft. if each side is lengthened by four feet. how could the perimeter of the new square be xalculated

Area of a square=length times lenght or legnth^2
area=36 so legnth=√36=6
perimiter of square=legnth times 4 since all sides are same legnth
if each side legnthened by 4 feet then
original premiter=4 times 6=24
new perimiter=4 times (6+4)=4 times (10)=40
the new perimiter is 40 ft

It should be c i think.