a. Define macro variables, a and b and obs with values -2 and 2 and 1000 respectively. Write a data step program that uses these macro variables to generate 1,000 observations from a uniform(a,b) distribution. b. Use a PROC means step to examine the mean, minimum and maximum values of the sample generated and check that these are consistent with being from a uniform(-2,2) distribution. c. Include a modified version of your DATA step in a macro definition, unif_a_b, that generates the data step SAS code to generate a specified number of observations from a uniform(a,b) distribution (a