biostatistics

.A certain type of light bulb is advertised to last 1500 hours. The distribution of lifetimes for this type of light bulb is approximately normal with a mean of 1540 hours and standard deviation of 56 hours. a. What proportion this type of light bulb will last less than the advertised time? b. What proportion this type of light bulb will last longer than 1600 hours? c. What is the probability that a randomly selected light bulb of this type will last between 1625 and 1725 hours? d. Thirty six percent of light bulbs of this type will last longer than what value