Passage: While at G.E. during World War II, he developed a magnetron for radar jamming, which led to the development of the microwave oven.While studying the characteristics of p-i-n diodes used as power rectifiers, Hall had a key insight, which resulted in his being co-credited with William Shockley and W. T. Read, Jr., for the analysis of nonradiative carrier recombination in semiconductors. Hall developed the semiconductor laser in 1962, while working at General Electric in Schenectady, New York. In the 1970s, Hall's work focused on photovoltaics and solar cells. He retired in 1987, having been granted 43 U.S. patents during his career.

Question: How many patents did he have by the time he retired?
43