In a species of plant, flower colour is determined by two unlinked genes, $A/a$ and $B/b$, that assort independently.

• The dominant allele $A$ is required for the synthesis of a green precursor. Homozygous recessive ($aa$) individuals cannot synthesise this precursor, resulting in white flowers.
• The dominant allele $B$ codes for an enzyme that converts the green precursor into a blue pigment. The recessive allele $b$ codes for a non-functional enzyme, leaving the precursor green.

A genetic cross is performed between two double heterozygous plants ($AaBb\times AaBb$).

Which of the following correctly identifies the expected phenotypic ratio of the offspring?