What is the present value of: $($Use a Financial calculator to arrive at the answers. Enter all values as positive. Round the final answers to nearest whole dollar.$)$

a$.$ $$8,400$ in $6$ years at $8$ percent?

Present value $

b$.$ $$21,000$ in $8$ years at $13$ percent?

Present value $

c$.$ $$30,000$ in $15$ years at $10$ percent?

Present value $

d$.$ $$1,000$ in $20$ years at $19$ percent?

Present value $