Using Laravel Eloquent to return multiple table columns once and a sum of another column

I have a table in my database called stocks. In the table, i have two columns product_id, supplied among other columns. So when i get a supply, i add the entries to my table and the table looking like so;

product_id             supplied
1                         10
2                         15
5                          5
2                         12
4                         10
5                         12
2                          5
1                         12
4                         12

Now i want to use laravel eloquent to select the stock by the product_id, returning the total number of items in stock like this;

product_id       total_in_stock
    1                22
    2                32
    4                22
    5                17

Any assistance will be appreciated.

via Chebli Mohamed