Twin brothers, billy and bobby, can mow their grandparent's lawn together in 89 minutes. billy could mow the lawn by himself in 40 minutes less time that it would take bobby. how long would take bobby to mow the lawn by himself?

The accompanying normal probability plot was constructed from a sample of 30 readings on tension for mesh screens behind the surface of video display tubes used in computer monitors. does it appear plausible that the tension distribution is normal? the given probability is has a significant downward curve, so it is plausible that the tension distribution is normal. the given probability is has a significant downward curve, so it is not plausible that the tension distribution is normal. the given probability is quite linear, so it is plausible that the tension distribution is normal. the given probability is has a significant upward curve, so it is not plausible that the tension distribution is normal. the given probability is quite linear, so it is not plausible that the tension distribution is normal.