Final answer:
To calculate the after-tax cost of each payment for a self-employed calendar-year taxpayer, multiply each payment by (1 - marginal tax rate).
Step-by-step explanation:
To calculate the after-tax cost of each payment, we need to multiply each payment by (1 - marginal tax rate). In this case, Haru's marginal tax rate is 37%, so the after-tax cost of each payment would be 63% of the original payment.
For example, if a payment is $100, the after-tax cost would be $100 * (1 - 0.37) = $63.
Apply this calculation to each cash payment Haru made to find the after-tax cost.