In a Wheatstone bridge circuit, `P=7 Omega, Q= 8 Omega, R = 12 Omega and S = 7 Omega`. Find the additional resistance to be used in series with `S` , so that the bridge is balanced.
Options:
(a) `6.72 Omega`
(b) `7.62 Omega`
(c) `2.67 Omega`
(d) `6.27Omega`