‘Cosby Show’ Back to No. 1

NEW YORK — “The Cosby Show” rebounded into first place, albeit tied with its spinoff, “A Different World,” and NBC was first in the ratings despite a lot of prime-time news preemptions last week, according to Nielsen ratings released today.

Two of the prime-time news shows--the one-hour “Conversation With Mikhail S. Gorbachev” on Monday and the half-hour, four-network interview with President Reagan on Thursday--weren’t included in the ratings because they weren’t sponsored. The two-hour “America’s Future--A Presidential Debate” on Tuesday was sponsored and ranked 58th out of 70 programs.