Assume a length of DNA that has just one replication origin at its centre and is 3 billion nucleotide pairs in length with a replication speed of 100...

Assume a length of DNA that has just one replication origin at its centre and is 3 billion nucleotide pairs in length with a replication speed of 100 nucleotides per second. How long would it take to replicate? How many equally spaced replication origins would be needed if the DNA were to be replicated in 24 hours ?