If a variable line, 3x + 4y – λ = 0 is such that the two circles x2 + y2 – 2x – 2y + 1 = 0 and x2 + y2 – 18x – 2y + 78 = 0 are on its opposite sides, then the set of all values of l is the interval :
(1) (23, 31)
(2) {12, 21]
(3) (2, 17)
(4) [13, 23]
