Christina is using her computer to design invitations to her birthday party. The text of the invitation is contained in a rectangle with a length of 7.5 inches and a width of 5 inches. Around the perimeter of the text, Christina wants to have a red border of width r. Around the red border, she wants a purple border of width p. Find an expression for the perimeter of the completed invitation.
25 + 8r + 8p
37.5 + 6r + 2p
15 + 8r + 8p
12.5 + 4r + 4p