Write a Python function that takes two parameters: distance $($in kilometres$)$ and weight $($in kilograms$).$ The function should calculate and return the shipping cost based on the following criteria:

$$ For distances less than or equal to $50$ kilometres, the shipping cost is R$.$O$.5$ per kilogram.

$$ For distances greater than $50$ kilometres, the shipping cost is R$.$O$.7$ per kilogram.

Write a main function to test the defined function by prompting the user to input the distance. Then, randomly generate the weight of the package $($between $5$ and $100$ kg$).$ Finally, call the defined function above with these inputs and print the total shipping cost.