The coding part of the mRNA would be 750 bases long. However, the mRNA would be much longer than this in real life as there would be both a 3 prime and 5 prime untranslated region. The lenght of the untranslated regions varied depending on the protein in question, the organism it is from and even the location in which it is produced in that organism! In summary, it is impossible to answer this question.

three is prime

nine equals three times three

Introns (the stuff between the exons), and UTR (Untranslated region, the stuff before the start codon, and after the stop codon).

It is prime.

prime