A cat rides a merry-go-round while turning with uniform circular motion. At time t1 = 2.00 s, the cat's velocity is v1 = (5.50) + (4.00 m/s) , measured on a horizontal xy coordinate system. At time t2 = 9.00 s, a half-revolution later, its velocity is v2 = (-5.50 m/s) + (-4.00 m/s) .

a) What is the magnitude of the cat's centripetal acceleration

b) What is the magnitude of the cat's average acceleration during the time interval t2 - t1?