In 1970, it was reported that 16% of babies were delivered by Cesarean section, 10% were delivered with assisted delivery, and 74% were delivered via unassisted delivery. A sample taken in 2017 of 150 live births found that 45 of them were done via Cesarean section, 25 by assisted delivery, and 80 by unassisted delivery.

a) Construct a pie graph for the distribution of deliveries in 2017.

b) Test the claim that the distribution of delivery methods in 2017 has changed since 1970, using a significance level of 0.01.