The authors of the article ‘a probabilistic insulation life model for combined thermal-electrical stresses" (ieee trans. onelect. insulation, 1985: 519—522) state that "the weibull distribution is widely used in statistical problems relating to agingof solid insulating materials subjected to aging and stress." they propose the use of the distribution as a model for time (inhours) to failure of solid insulating specimens subjected to ac voltage. the values of the parameters depend on thevoltage and temperature; suppose a and b = 200(values suggested by data in the article).a. what is the probability that a specimen's lifetime is at most 250? less than 250? more than 300? b. what is the probability that a specimen's lifetime is between 100 and 250? c. what value is such that exactly 50% of all specimens have lifetimes exceeding that value?