Let f(x, y) = k when 8 ≤ x ≤ 12 and

Let f(x, y) = k when 8 ≤ x ≤ 12 and 0 ≤ y ≤ 2 and zero elsewhere. Find k. Find P(X ≤ 11, 1 ≤ Y ≤ 1.5) and P(9 ≤ X ≤ 13, Y ≤ 1).