Write a function, computePrice(), that takes as two parameters: the age group and the ticket type, and returns the price for admission to the American Museum of Natural History. If the ticket type is "admission" and the age group is "adult", the price is $23. If the ticket type is "admission" and the age group is "child", the price is $13. If the ticket type is "admission" and the age group is "senior", the price is $18. If the ticket type is "+exhibitions" and the age group is "adult", the price is $33. If the ticket type is "+exhibitions" and the age group is "child", the price is $20. If the ticket type is "+exhibitions" and the age group is "senior", the price is $27. If the ticket type or age group are not one of the above, it returns -1.