4-2. There are several packages with apples. Each contains either 12 or 6 apples. How many apples can there be in total if it is known that there are no fewer than 70 and no more than 80? List all the options.
Answer: 72 or 78.

Solution. The number of apples in each bag is divisible by 6, so the total number of apples is also divisible by 6. In this range, there are only two numbers divisible by $6:$ these are 72 and 78.