Develop a well-structured function to determine the elapsed days in a year. The first line of the function should be set up as function nd = days(mo, da, year) where mo = the month (1-12), da = the day (1-31) and year = the year. Test it for January 1, 1999; February 29, 2000; March 1, 2001; June 21, 2002; and December 31, 2004. 2.21 Manning's equation can be used to compute the velocity of water in a rectangular open channel,