The weights of 4 boxes are 70, 50, 30 and 90 kilograms. Which of the following cannot be the total weight,in kilograms, of any combination of these boxes and in a combination a box can be used only once?
P, Q, R, S and T are standing in a line. P is taller than S but shorter than Q. T is shorter than S but taller than R. Who is the second tallest of them all?