The branch of CBS News that produces newscasts and features to radio stations is CBS News Radio. The radio network is the oldest unit of CBS and traced its roots to the company's founding in 1927, and the news division took shape over the decade that followed. The list of CBS News correspondents  includes those reporting on CBS News Radio. CBS News Radio produces the oldest daily news show on radio or television, the CBS World News Roundup, which first aired in 1938 and celebrates its 80th anniversary in 2018. The World News Roundup airs twice every weekday: a morning edition is anchored by Steve Kathan and produced by Paul Farry, while a "late edition" is anchored by Dave Barrett and produced by James Hutton. The evening Roundup, previously known as The World Tonight, has aired in its current form since 1956 and has been anchored by Blair Clark, Douglas Edwards, Dallas Townsend and Christopher Glenn . The CBS Radio Network provides newscasts at the top of the hour, regular updates at :31 minutes past the hour, the popular Newsfeeds for affiliates  at :35 minutes past the hour, and breaking news updates when developments warrant, often at :20 and :50 minutes past the hour. Skyview Networks handles the distribution.
Question: How many anchors has the evening Roundup had?
Answer: 4