Please answer the following question: Given the following context:  As The Five's campaign against Rubinstein continued in the press, Tchaikovsky found himself almost as much a target as his former teacher. Cui reviewed the performance of Tchaikovsky's graduation cantata and lambasted the composer as "utterly feeble.... If he had any talent at all ... it would surely at some point in the piece have broken free of the chains imposed by the Conservatory." The review's effect on the sensitive composer was devastating. Eventually, an uneasy truce developed as Tchaikovsky became friendly with Balakirev and eventually with the other four composers of the group. A working relationship between Balakirev and Tchaikovsky resulted in Romeo and Juliet. The Five's approval of this work was further followed by their enthusiasm for Tchaikovsky's Second Symphony. Subtitled the Little Russian (Little Russia was the term at that time for what is now called the Ukraine) for its use of Ukrainian folk songs, the symphony in its initial version also used several compositional devices similar to those used by the Five in their work. Stasov suggested the subject of Shakespeare's The Tempest to Tchaikovsky, who wrote a tone poem based on this subject. After a lapse of several years, Balakirev reentered Tchaikovsky's creative life; the result was Tchaikovsky's Manfred Symphony, composed to a program after Lord Byron originally written by Stasov and supplied by Balakirev. Overall, however, Tchaikovsky continued down an independent creative path, traveling a middle course between those of his nationalistic peers and the traditionalists.  answer the following question:  What was the name of Tchaikovsky's former teacher?
Answer:
Rubinstein