Texas Instruments BA35 Solar Calculator
With its preprogrammed financial and accounting functions, the Texas  Instruments BA35 calculator is designed for business professionals and students.  It features cash flow analysis and time-value-of-money and compound-interest  calculations. It can also recall time-value-of-money values as well as annuity  operations. It converts annual percentage rate (APR) to effective rate (EFF)  interest and does amortization balance, payment-to-interest, cost-sell-margin,  and markup calculations. Because the BA35 runs on solar power, you'll never have  to worry about replacing the batteries. It comes with a protective slide case,  guidebook, and a one-year limited warranty.