A wall is constructed of a 2 inch layer of fiberglass board (R = 8) and six inches of fiberglass batting (R = 19). If the temperature on the outside surface of the fiberglass board is 50degreesF and the temperature on the inside surface of the fiberglass batting is 68oF, what is the temperature (in degreesF) at the interface? (The units of R are ft2degreesF h/BTU.)