What is the exact title of the diploma piece without which Etty could not become a Royal Academician?  Answer the above question based on the context below:  In February 1828, shortly before his 41st birthday, Etty soundly defeated John Constable by 18 votes to five to become a full Royal Academician, at the time the highest honour available to an artist. By this time, complaints about his supposed indecency were beginning to resurface. All but one of the 15 paintings Etty exhibited at the Royal Academy in the 1820s had included at least one nude figure, and Etty was acquiring a reputation for using respectable themes as a pretext for nudity.For the 1828 Summer Exhibition Etty exhibited three pictures; The World Before the Flood, Venus, the Evening Star and Guardian Cherubs. (The latter was a portrait of the children of Welbore Ellis Agar, 2nd Earl of Normanton, and was the only non-nude painting exhibited by Etty at the RA in the 1820s.) Although similar to his earlier works, they were technically more accomplished. Both The World Before the Flood and Venus attracted positive reviews in the press and were sold during their exhibition for substantial sums, although the purchase by the Marquess of Stafford of The World Before the Flood—a work containing scantily clad figures of both sexes—drew a pointed comment in The Gentleman's Magazine that it "will serve to accompany the private Titians of that nobleman". Despite the increasing number of complaints in the press about his use of nudity, respect for Etty from his fellow artists continued to rise, and in 1828 the British Institution awarded him £100 in recognition of his talent. As soon as the 1828 Summer Exhibition was over, Etty stopped work on other projects to concentrate on a diploma piece, without which he could not become a Royal Academician. This piece, Sleeping Nymph and Satyrs, was presented to the Academy in October, and in December 1828 Etty became a Royal Academician. It appears to me then that virtuous happiness being our lawful aim in life, that having Academic Rank and Fame the next thing to be considered (if God approve) is to seek that Decent Competency which shall make my latter days comfortable...
A:
Sleeping Nymph and Satyrs