According to Philip Vernon, the proponent of the 'Hierarchical Theory of Intelligence', which factor occupies the highest apex in the human intellectual structure, and how does this theory establish coordination between Spearman's two-factor theory and Thurston's multi-factor theory?

Philip Vernon propounded the hierarchical theory of intelligence, which presents an excellent coordination between Charles Spearman's 'general factor' (g-factor) and Louis Thurstone's 'group factors'. At the highest apex of this model is general intelligence (g), below which are two major broad group factors: Verbal-Educational (v:ed) and Practical-Mechanical (k:m). These are subsequently divided into smaller sub-factors.