help with normal distribution question

hi, i'm having trouble understanding this normal distribution question. any help on how would you work this out.thanks

The present air-traffic volume at the City airport (number of takeoffs and landings) during the peak period has a normal distribution with a mean, μ, of 100 planes and a standard deviation, σ, of 20 planes

(a) If the present runway capacity (for takeoffs and landings) is 142 planes per hour, what is the current probability of air traffic congestion in the peak period? (that is, what is the probability that the volume exceeds capacity - assume just one peak period daily).

(b) If the peak period volume increases by 70 % over the next 10 years (that is, the peak period volume still has a normal distribution but the mean and standard deviation are both 70 % higher), what is the probability of peak period congestion if the runway capacity is unchanged from the present?

(c) If the projected growth is correct, what airport capacity is required 10 years from now if the current service level is to be maintained (that is the same probability of peak period congestion as at present.