When their child was born, her parents invested $40,000 in a plan guaranteed to increase by 3% per year. the logarithmic function y equals 77.9 log start fraction x over 40,000 end fraction can be used to determine the number of years, y, it takes for the investment to be worth x dollars.

exponential graph modeling the equation y equals seventy seven point nine times the log of the quantity x over forty thousand. graph comes up from the left along the y axis and goes through the point forty thousand comma zero and continues to the right towards infinity.

after how many years will the investment be worth approximately 75% more than it was originally and how old will their child be when the investment is worth about $80,000?

the investment is worth approximately 75% more after 19 years, and the investment is worth $80,000 when their child is about 23 years old.
the investment is worth approximately 75% more after 4 years, and the investment is worth $80,000 when their child is about 25 years old.
the investment is worth approximately 75% more after 14 years, and the investment is worth $80,000 when their child is about 31 years old.
the investment is worth approximately 75% more after 27 years, and the investment is worth $80,000 when their child is about 19 years old.