Rectangle A′B′C′D′ is the image of rectangle ABCD after a dilation centered at point P.

Rectangle A B C D with B C equals 42 inches and D C equals 30 inches. Below rectangle A B C D is point P and below point P is rectangle A prime B prime C prime D prime with B prime C prime equals 35 inches and D prime C prime equals 25 inches. There are four dashed lines. They pass through A, P and A prime, B, P, and B prime, C, P, and C prime, and D, P and D prime.

What scale factor was used in the dilation?

Enter your answer, as a simplified fraction, in the box.