The speed limit in school zones actually varies a fair amount state by state. Unless otherwise posted the speed limit in school zones in the District of Columbia, where Abby would be taking the driving test, is 15 miles per hour. However DC is located within the states of Maryland and Virginia. The speed limit for school zones in Maryland (unless posted otherwise) is 35 miles per hour when there is a crossing guard present, and 25 miles per hour when there is no crossing guard. In Virginia the school zone speed limit (unless posted otherwise) is 25 miles per hour at all times.
The trivia items below may give away important plot points.
Tony is told by an on-line genetic research firm (for a fee, of course) that he is related to British nobleman "Archibald Drummond, the 17th Earl of Trent", but later finds out that "some historians" think Drummond may have been Jack the Ripper.
Tony's putative ancestor, Archibald Drummond, 17th Earl of Trent (no such title, FWIW), is shown in a painting in clothing contemporary with the Napoleonic wars, through about 1930. Shown as an adult of at least 30 yo, thus born around 1800, there is no possibility that he could still be alive, or at least in any shape at 88-91, to have been a suspect for an infamous murderer, whose murders were committed from October 1888 to February 1891.