The r-chart:
a. generally uses control limits set at plus or minus 2 standard deviations of the distribution, rather than plus or minus 3 which is commonly used on the x-bar chart.
b. control limits are computed using sample standard deviations.
c. is used to measure changes in the central tendency.
d. is used to indicate gains or losses in uniformity.

i think it is

step-by-step explanation:

a formal letter is a letter the you would send to a king

idk bring the function back   im not smart

step-by-step explanation:

30 miles

step-by-step explanation:

we know that 60 seconds equals 1 minute and 60 minutes 1 hour

44 ft       60 sec     60 min     158400   ft

  *   *   =

1 sec       1 min       1 hour         hour

we know that there are 5280 ft per mile

158400   ft       1 mile         30 miles

  *   =

1   hour               5280 ft     1 hour

so in 1 hour   it can travel 30 miles