A child of chronological age 10 years who successfully passes all the test items passed by most 6-year-old children is considered to have a mental age of:

A 4-year-old, Mary, has a ratio IQ score of 200. An 8-year-old, Jimmy, has an IQ score of 100. A 10-year-old, Johnny, has an IQ score of 90. Based on the formula IQ = (Mental Age / Chronological Age) × 100, which child has the highest mental age?