The Kollar Company has a defined benefit pension plan. Pension information concerning the fiscal years $2024$ and $2025$ are presented below $($$ in millions$)$:

Information Provided by Pension Plan Actuary:

Projected benefit obligation as of December $31,2023=$ $$3,200.$

Prior service cost from plan amendment on January $2,2024=$ $$600($straight$-$line amortization for $10-$year average remaining service period$).$

Service cost for $2024=$ $$640.$

Service cost for $2025=$ $$690.$

Discount rate used by actuary on projected benefit obligation for $2024$ and $2025=10\%.$

Payments to retirees in $2024=$ $$500.$

Payments to retirees in $2025=$ $$570.$

No changes in actuarial assumptions or estimates.

Net gain$$AOCI on January $1,2024=$ $$370.$

Net gains and losses are amortized for $10$ years in $2024$ and $2025.$

Information Provided by Pension Fund Trustee:

Plan asset balance at fair value on January $1,2024=$ $$2,300.$

$2024$ contributions $=$ $$660.$

$2025$ contributions $=$ $$710.$

Expected long$-$term rate of return on plan assets $=12\%.$

$2024$ actual return on plan assets $=$ $$210.$

$2025$ actual return on plan assets $=$ $$260.$

Required:

Calculate pension expense for $2024$ and $2025.$

Prepare the journal entries for $2024$ and $2025$ to record pension expense.

Prepare the journal entries for $2024$ and $2025$ to record any gains and losses and new prior service cost.

Prepare the journal entries for $2024$ and $2025$ to record $($a$)$ the cash contribution to plan assets and $($b$)$ the benefit payments to retirees