On interchanging the resistances, the balance point of a meter bridge shifts to the left by 10 cm. The resistance of their series combination is $1\; K \Omega$. How much was the resistance on the left slot before interchanging the resistances ?

Question

( A ) $990 \Omega$
( B ) $505 \Omega$
( C ) $550 \Omega$
( D ) $910 \Omega$