The average 30-year fixed mortgage rate in the United States in the first week of May in 2010 through 2012 is approximated by 55.9 M(t) = 0.31t+ 11.2 percent/year. Here t is measured in years, with t = 0 corresponding to the first week of May in 2010.+ (Round your answers to one decimal place.) (a) What was the average 30-year fixed mortgage rate in the first week of May in 2013 (t = 3)? % (b) How fast was the 30-year fixed mortgage rate changing in the first week of May in 2013 (t = 3)? %/year