In the England-New Zealand one day match, due to rain, England needed 324 runs in 48 overs to win. In initial 10 overs, the average scoring rate was 6, but in next 10 overs it increased to 8.5. It then declined to 5.5 in next 10 overs and again rose to 7 in next 10 overs. To win the match now what average is needed?