Delta Corporation sponsors a defined benefit pension plan for its employees. At the beginning of the year, the projected benefit obligation (PBO) was $1,500,000, and the fair value of plan assets was $1,200,000. The company's actuary estimates a service cost of $100,000 and an interest cost of $90,000 for the year.

Calculate the pension expense for Delta Corporation for the year and prepare the journal entry to record the pension expense. Additionally, discuss the impact of changes in actuarial assumptions on pension accounting.