How fast was the earth rotating 3.5 billion years ago?

Calling all math nerds! I have a math problem I need help solving. According to Leslie Morrison, an astronomer now retired from the Royal Observatory Greenwich in London, the earth’s spin has slowed by about 6 hours in the past 2,740 years, Morrison and his team reported this finding in the Proceedings of the Royal Society A. This means that the farther back in time we go, the faster the earth would be spinning. What I want to know is this: assuming that the decrease in the earth’s rotation speed has been constant if the earth is currently spinning at approximately 1,000 mph at the equator, how fast would it be spinning A)2.5 million years ago(when the supposed evolutionary chimp line diverged from the human line) B)65 million years ago(when dinosaurs supposedly went extinct) C)3.5 billion years ago (when the first life supposedly appeared on earth) D)4.5 billion years ago (when earth supposedly formed). The reason I ask is that I’m skeptical that life could exist on earth if the rotation was too fast in the distant past. Educateforlife.org