A maths professor asked one of his students to visit his house regarding some work. The student asked the professor his house number. The professor replied in a strange way : 1. If my house number is a multiple of 3, then it is a number from 50 to 59. 2. If my house number is not a multiple of 4, then it is a number from 60 to 69. 3. If my house number is not a multiple of 6, then it is a numbre from 70 to 79. Can you determine the professor's house number ?