6. (6 pts) The batteries used by a calculator have useful lives that follow a normal distribution, with a mean of 1000 hours and a standard deviation of 200 hours. (a) Find the range of middle 95% batteries useful life. (b) A random sample of 100 batteries is drawn. Find the range of middle 95% sample means of batteries useful life.

Use the following statements to write a compound statement for the conjunction or disjunction. then find its truth value. p: an isosceles triangle has two congruent sides. q: a right angle measures 90° r: four points are always coplanar. s: a decagon has 12 sides. a) a right angle measures 90° or an isosceles triangle has two congruent sides; true. b) a right angle measures 90° and an isosceles triangle has two congruent sides; true. c) a right angle measures 90° and an isosceles triangle does not have two congruent sides; false. d) a right angle measures 90° or an isosceles triangle does not have two congruent sides; true.