The concentration y of a certain drug in the bloodstream t hours after an oral dosage (with 
) is given by the equation 
How long does it take for the concentration to reach 90? Round your answer to two decimal places.
Definitions:
Raymond Cattell
A psychologist known for his work in personality theory and the development of several personality assessments.
Francis Crick
A British scientist known for co-discovering the structure of the DNA molecule with James Watson.
Crystallized Intelligence
The capability of applying knowledge and experiences that one has learned over time.
Triarchic Intelligence
A theory by Robert Sternberg that intelligence consists of analytical, creative, and practical aspects.
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