Durham began a defined-benefit pension plan for its employees on January 1, 2018. The following data are provided for 2018, as of December 31, 2018: Projected benefit obligation $600,000; Accumulated benefit obligation $490,000; Plan assets at fair value $540,000; Pension expense $70,000; Employers cash contribution (end of year) $110,000. What amount should Durham report as a net pension liability at December 31, 2018?

a. $50,000 b. $60,000 c. $80,000 d. $130,000