A substation operating at 33kv is divided into sections A and B. Section A consist of three generators 15MVA each having a reactance of 15% and section B is fed from the grid through a 75MVA transformer of 8% reactance. The circuit breakers have each a rupturing capacity of 750MVA.Determine the reactance of the reactor to prevent the breakers being overloaded if a symmetrical short circuit occurs on an outgoing feeder connected to A.