Input is a matrix including service time and probability of service time. Another input is a random number. Function should transform the random number to service time.

First column of the input1 is service time and second column is probability of that service time.

input1 = [
2 0.4
5 0.4
9 0.2]

We can calculate cumulative probability and Random Number Assignment with this input,

   Service                      Cumulative       Random Number
   Time        Probability      Probability      Assignment
     2             0.4              0.4          0.000 - 0.400
     5             0.4              0.8          0.400 - 0.800
     9             0.2              1.0          0.800 - 1.000

input2 is a random number between 0 and 1 such as;

   input2 = 0.125

Random number can be transformed to service time with the table. Random number (input2) is between first line of random number assignment

0.000 < Random number <= 0.400

as a result

   serviceTime = 2

Note: You can assume that the sum of the probabilities will be equal to one.