Please provide explanations.

The Silver Copper Company sponsors a defined benefit pension plan. The following information pertains to that plan ($ in millions): Projected benefit obligations at January 1, 2021, $150 million; Service cost for 2021, $42 million; Retiree benefit paid (end of year), $60 million; Loss due to changes in actuarial assumptions, $10 million. The actuary's discount rate was 10%. What is the amount of the projected benefit obligation at December 31, 2021? a. $148 million b. $142 million c. $157 million d. $137 million