Exon one has 570 nucleotides. Exon three has 810 nucleotides. We are not concerned about exon two because it is spliced out in the variant. There are 1380 nucleotides (570+810). Each amino acid requires three nucleotides. One codon, or three nucleotides, codes for one amino acid. So 1380/3=690 amino acids.
I believe it’s called a climax community! hope this helped :)