Question 251151
To get the maximum value of x(y-z), we have to choose the values such that x has a maximium value ans (y-z) has a mazimum value.
The given numbers are 60,85,90,105,120. The maximum value of (y-z) = 60, if we choose z=120 and y = 60. 
Then choose the maximum value from other three numbers as x.
Therefore we choose x = 105.
Sothe maximum value of x(y-z) = 105x60 = 6300