Article: Mikhail Gorbachev was elected General Secretary by the Politburo on March 11, 1985, three hours after predecessor Konstantin Chernenko's death at age 73. Gorbachev, aged 54, was the youngest member of the Politburo. His initial goal as general secretary was to revive the Soviet economy, and he realized that doing so would require reforming underlying political and social structures. The reforms began with personnel changes of senior Brezhnev-era officials who would impede political and economic change. On April 23, 1985, Gorbachev brought two protégés, Yegor Ligachev and Nikolai Ryzhkov, into the Politburo as full members. He kept the "power" ministries happy by promoting KGB Head Viktor Chebrikov from candidate to full member and appointing Minister of Defence Marshal Sergei Sokolov as a Politburo candidate.

Question: To which two people did Gorbachev grant membership into the Politburo for his own reasons?
Yegor Ligachev and Nikolai Ryzhkov,