Which of the following items comprises the largest resource cost incurred directly by taxpayers to comply with the US tax system (i.e., figuring and paying their taxes)?

money spent on accountants and tax preparers

money spent on tax software programs

money spent on tax guides and help sources

costs incurred by employers to withhold and pay taxes on behalf of their employees

costs of employers to provide information to the IRS

the time taxpayers spend on preparing their taxes and collecting necessary documentation

the costs incurred by the IRS to monitor and audit taxpayers who fail to file returns