Please help me with these questions

. The lifetime of a certain brand of light globe is normally distributed with a mean of 400 hours and standard deviation of 50 hours. (a) Find the probability that a randomly chosen light globe will last more than 375 hours. (3 marks) (b) The light globes are sold in a boxes of ten. Find the probability that at least nine of the globes in a randomly selected box will last more than 375 boxes. (3 marks) . Let X be a normally distributed random variable with a mean of 6 and variance of 4. Let Z be a random variable with the standard normal distribution (a) Find P(X > 6). (2 marks) (b) Find In such that P(X > 7) = P(Z