I took some approaches from different methods and I understand how to construct a spreadsheet based on the question but when i take the difference of both NPV's it says that it is the wrong answer. Below is the question and my answer. Please help reconcile this immediate issue. I gratefully appreciate it.

Question:

Better Mousetraps has developed a new trap. It can go into production for an initial investment in equipment of $6.6 million. The equipment will be depreciated straight-line over 6 years, but, in fact, it can be sold after 6 years for $643,000. The firm believes that working capital at each date must be maintained at a level of 15% of next years forecast sales. The firm estimates production costs equal to $1.90 per trap and believes that the traps can be sold for $6 each. Sales forecasts are given in the following table. The project will come to an end in 6 years, when the trap becomes technologically obsolete. The firms tax bracket is 40%, and the required rate of return on the project is 12%

Year: Sales (millions of traps) 0 0 1 0.4 2 0.5 3 0.7 4 0.7 5 0.5 6 0.3 Thereafter 0 Suppose the firm can cut its requirements for working capital in half by using better inventory control systems. By how much will this increase project NPV? (Do not round your intermediate calculations. Enter your answer in millions rounded to 4 decimal places.) Answer is complete but not entirely correct. Change in NPV 19,285.7143 million