Definition: In this task you will be given a list of lists, of numbers. For every inner list, you should multiply every number in that list and put the results in your answer. The output should be a list of numbers with the same length as the number of the lists in the input list.
Input: [[-40, -12], [9, -39], [-21, 12, -1, 31]]

[480, -351, 7812]