URGENT Please help solve this probability question

A single spark plug engine comes with spark plug A installed. A spare spark plug B is provided with the engine, but differs from the original due to supplier constraints. If spark plug B is installed after the failure of spark plug A, what is the probability that the total lifetime of the two spark plugs is more than 2000 hours? Spark plug A has a lifetime that is normally distributed with mean 790 hours and standard deviation 100 hours. Spark plug B has a lifetime that is normally distributed with mean 910 hours and standard deviation 150 hours. Assume that the lifetimes of the spark plugs are independent. unu- mun-u. n u a...- man. an nun mam -un um an um-m mm mu .1. o-am unn- mu m um:- unu- um mm .mm wn- tan-n no. man: boo-I In: no. nun-m am.. an .0 uni-u I- I. .u out.\" man Select one: Q a. 0.0262 0 b. 0.2033 0 0. 0.0132 0 d. 0.1335 0 e. 0.3397 Of. 0.2912 0 g. 0.0485