Arectangle has a length of 1.4 feet and a width of 1.2 feet. what is the effect on the perimeter of this rectangle if the length and width are doubled?

Hello : 
the perimetre is :  3(1.4+1.2) = 5.2 feet
if the length and width are doubled the perimeter is : 2(1.2+2(1.2)) =7.2 feet
 the effect on the perimeter add : 2

The answer to the question is d