Question: What sovereign duke of the Duchy of Saxe-Coburg and Gotha, composed the opera Diana von Solange in 1858?
Sentence (from "Alfred, Duke of Saxe-Coburg and Gotha"): Alfred (Alfred Ernest Albert; 6 August 184430 July 1900) reigned as Duke of Saxe-Coburg and Gotha from 1893 to 1900.
Relevant evidence: No