text: 
  
  # n trades m tries
  n,m = map(int,input().split())
  
  #profit probability
  P = list(map(float,input().split()))
  
  # profit chances
  profit = list(map(float,input().split()))
  
  #loss chances
  loss = list(map(float,input().split()))
  
  check_all  = [0]*n 
  
  for i in range(n):
      check_all[i] = (P[i]*profit[i])-((1-P[i])*loss[i])
  
  check_all.sort(reverse=True) 
  
  answer=0
  for i in range(m):
      if check_all[i]<0:
          break 
      answer+=check_all[i] 
  if "." in str(answer)[-2]:
      answer=str(answer)+"0"
      print(answer)
  else:
      print(round(answer,2))