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1) Write a function definition for a user-defined function that calculates the (floating-point double) Percent Difference between two experimental double values, A and B. Percent Difference - A -B PA * 100% (4 22) 2) Write a function definition for a user-defined function that calculates the (floating-point double) Percent Error between a known double value, A, and an experimental double value B Percent Error +100% 3) Write a function definition for a user-defined function that calculates the (floating-point double) mean of a specified column in a 2-D array that has NROWS rows and NCOLS columns. (NROWS and NCOLS are pre-defined symbolic constants) The parameters should be the double array and the desired column, as specified in the following function prototype double col mean (double x[NROWS , NCOLS), ?nt col) ; 4) Same as #3, but calculating the standard deviation rather than the mean (xi -Xavg