How do you calculate present value with a Texas instrument calculator (BA II Plus).
Example: Annual payments are:
Dec. 31/ 2xx1 $6,000
Dec.31/2xx2 6,000
Dec31/2xx3 6,000
Dec31/2xx4 10,000
interest rate is 6% compounded semi-annually.

See ABC Co example starting at bottom of page 31. http://education.ti.com/guidebooks/financial/baiiplus/BAIIPLUSGuidebook_EN.pdf

In your case you don't have an "original cost" to deal with; just compute the PV of the CFs as shown in the example.