David Rock's House Number
David's house has a number.
1) If the house number is a multiple of 3, then it is a number from 50 to 59
2) If the house number is NOT a multiple of 4, then it is a number from 60 to 69
3) If the house number is NOT a multiple of 6, then it is a number from 70 to 79
What is the house number?