Commercial solar water heaters began appearing in the United States in the 1890s. These systems saw increasing use until the 1920s but were gradually replaced by cheaper and more reliable heating fuels. As with photovoltaics, solar water heating attracted renewed attention as a result of the oil crises in the 1970s but interest subsided in the 1980s due to falling petroleum prices. Development in the solar water heating sector progressed steadily throughout the 1990s and growth rates have averaged 20% per year since 1999. Although generally underestimated, solar water heating and cooling is by far the most widely deployed solar technology with an estimated capacity of 154 GW as of 2007.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): Since 1999, what average rate has the solar water heating sector progressed at?
Ah, so.. 20% per year

The San Diego Surf of the American Basketball Association is located in the city. The annual Farmers Insurance Open golf tournament (formerly the Buick Invitational) on the PGA Tour occurs at Torrey Pines Golf Course. This course was also the site of the 2008 U.S. Open Golf Championship. The San Diego Yacht Club hosted the America's Cup yacht races three times during the period 1988 to 1995. The amateur beach sport Over-the-line was invented in San Diego, and the annual world Over-the-line championships are held at Mission Bay every year.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): How many times were the America's Cup yacht races hosted by the San Diego Yacht Club from 1988 to 1945?
Ah, so.. unanswerable

The Russian alphabet has many systems of character encoding. KOI8-R was designed by the Soviet government and was intended to serve as the standard encoding. This encoding was and still is widely used in UNIX-like operating systems. Nevertheless, the spread of MS-DOS and OS/2 (IBM866), traditional Macintosh (ISO/IEC 8859-5) and Microsoft Windows (CP1251) created chaos and ended by establishing different encodings as de facto standards, with Windows-1251 becoming a de facto standard in Russian Internet and e-mail communication during the period of roughly 19952005.
If it is possible to answer this question, answer it for me (else, reply "unanswerable"): During what period was MS-DOS created?
Ah, so..
unanswerable