An oak tree that is 220 years old produced acorns at two different rates. until it reached maturity, it produced an average of 900 acorns a year. however, once the tree reached maturity, it produced an average of 2200 acorns a year. one particular tree, angel oak, has produced about 289,000 acorns in its lifetime. at what age did it reach maturity?
a) 188
b) 150
c) 138
d) 148