. A radio manufacturer believes that the length of life of WPPX model radio is normal with µ=12 years and σ=2.5 years. (a) What percent of the radios will function for more than 16 years? (b) Suppose the company decides to replace 1% of the radios. Find the length of guarantee period. i.e. find X. (c) What percent of the radios that will fail to satisfy the guarantee period of 10 years? , i. e. less than 10 years? (d) If 10% of the radios will function for more than X years, find X.