Allen needs to calculate how much his investment has increased over the past year. He enters the original amount in cell B3 and the new amount in cell B4. He typed in the formula: =B3-B4. He estimated his answer to be 500 and the answer is not close. He should _____.
add the values in B3 and B4
ignore his estimation
multiply the values in B3 by B4
change the formula to =B4-B3