A rigging job calls for lifting a structure that weights IIS tons. Two cranes are available, one with a ted capacity of $75$ tons and the other with a capacity of $100$ tons. The total weight of the rigging required make the lift is $12$ tons, of which $8$ tons is to be carried by the larger crane and $4$ tons is to be carried by e smaller crane. If the cranes are to be loaded in proportion to their net capacities, what should the net ad on the $100-$ton crane be$?$

$86$ tons

$78$ loms

$72tans$

$65$ lons