One of the following four-digit numbers is not divisible by 4: 3544, 3554, 3564, 3572, 3576. What is the product of the units digit and the tens digit of that number?
A number is divisible by 4 if its last two digits are divisible by 4. The only given number that is not divisible by 4 is 3554 because 54 is not divisible by 4. The product of the units digit and the tens digit of 3554 is $5\cdot 4=\boxed{20}$.