Assume that Hartmann Company contributes 15% of employee monthly salaries to an employee 401k plan. Assuming $600,000 of monthly salaries, the journal entry to record the monthly contribution would include a __________ to __________ for $90,000.

a. debit; Pension Expense
b. debit; Cash
c. debit; Unfunded Pension Liability
d. credit; Unfunded Pension Liability