In this task, you're given a question, along with a context passage which has extra information available on certain terms mentioned in it. Your job is to determine which sentence(s) from the passage can be used to search for further information needed to answer the question.

Question: What age was Kronecker when he recommended Selling for a post at the University of Wurzburg? Passage:Selling studied mathematics at the Universities of Göttingen and Munich (under Philipp Ludwig von Seidel). He obtained the doctorate in Munich in 1859, under the supervision of Bernhard Riemann. On recommendation of Leopold Kronecker he became professor extraordinarius of mathematics at the University of Würzburg in 1860 – against the will of the philosophical faculty and the mathematics professor Aloys Mayr. There, he also taught astronomy and became conservator-restorer at the astronomical department in 1879. In 1873 he wrote an important paper on binary and ternary quadratic forms which was also translated into French and cited by Henri Poincaré, Émile Picard and Paul Gustav Heinrich Bachmann. Beginning with 1877 he also became concerned with insurance, and participated in the reorganization of the pensions in Bavaria on behalf of the Bavarian government. His application for a promotion to professor ordinarius was declined in 1891. In 1906 he became emeritus.

On recommendation of Leopold Kronecker he became professor extraordinarius of mathematics at the University of Würzburg in 1860 – against the will of the philosophical faculty and the mathematics professor Aloys Mayr