Jon should report his answer to one significant digit only.
When several numbers are multiplied, the number of significant digits in the final answer is determined by the number that has the least number of significant digits.
In this case, 1 has only one significant digit, whereas 2.0 has two, 3.00 has three, and 4.000 has four significant digits. Hence, 1 strongly affects the number of significant figures in the answer.
