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Frank:

Thank's for the suggestion. One problem, likely a failing on my part, algebraic calculators and yours truly have never really gotten along. About 30 years ago, I came upon the HP 11C. I bought one of them, and used it ever since, though since retiring, it is much less used. Unfortunately, there never was a solar powered version, but in my experience, when I used mine just about every day, a set of batteries lasted about 3 years. They cost less than $10. The batteries in it now were installed in September, 2015, and show no signs of running down. As above noted, they are little used these days. By the way, HP also made a financial calculator, the 12C, which physically looked like a twin of the 11C. A while back, the 12C celebrated it's 50th year of production. For some reason, the 11C was produced for just a few years, who knows why.

Thanks for your thoughts, and by the way, a happy holiday season to you.