120. Based on data from a dart-throwing experiment, the article

“Shooting Darts” (Chance, Summer 1997, 16–19) proposed that the horizontal and vertical errors from aiming at a point target should be independent of one another, each with a normal distribution having mean 0 and variance 2

.

It can then be shown that the pdf of the distance V from the target to the landing point is f(v)

ev2/22 v 0

a. This pdf is a member of what family introduced in this chapter?

b. If
20 mm (close to the value suggested in the paper), what is the probability that a dart will land within 25 mm

(roughly 1 in.) of the target?