The number of pumps in use at both a six-pump station and a four-pump station will be determined. Give the possible values for each of the following random variables: (a) T = the total number of pumps in use. (b) X = the di?erence between the numbers in use at stations 1 and 2. (c) U = the maximum number of pumps in use at either station. (d) Z = the number of stations having exactly two pumps in use.