please help this probability and statistics questions with clear step and details, thanks

(a) The distance, in metres, that a javelin can be thrown by boys at a school has a normal distribution with a mean of 45.50m and standard deviation of 15m. Calculate the probability that a pupil will throw the javelin a distance: i. greater than 55m (3 marks) ii. between 30m and 40m. (3 marks) iii. The school awards a certificate to each pupil who throws the javelin a distance greater than meters. Certificates are awarded to 15% of the pupils. Find the value of