Same rate implies linear increase, which we are told is 9000/year
 
 2010: profit of 45,000
 
 2011: profit of 45,000+9000 = 54,000
 
 2012: profit of 54,000 + 9000 = 63,000
 
 2013: profit of 63,000 + 9000 = 72,000
 
 2014: profit of 72,000 + 9000 = 81,000 <<<< This is the answer
 
 Note that we could have multiplied to get the same answer, but this way avoids fencepost problems: Okay because just a few years