Four resistances of 15$$\Omega $$, 12$$\Omega $$, 4$$\Omega $$ and 10$$\Omega $$ respectively in cyclic order to form Wheatstone's network. The resistance that is to be connected in parallel with the resistance of 10$$\Omega $$ to balance the network is _____$$\Omega $$.

The balancing length for a cell is 560 cm in a potentiometer experiment. When an external resistance of 10 $$\Omega $$ is connected in parallel to the cell, the balancing length changes by 60 cm. If the internal resistance of the ceil is $${N \over {10}}$$ $$\Omega $$ , where N is an integer then value of N is .............