Goal: Increment the value of a variable. Assignment: You are managing a wildlife reserve and keeping track of a particular bird species population. Each year, migratory birds join the local population, increasing the total count. Given the int variables named northernBirdPopulation and southernBirdPopulation, write some code that decreases the value of the first by 20 and increases the value of the second by 20 to account for the new arrivals during the migration season. Note: Be sure to use combined assignment operators in your code