Assume that there is a positive linear correlation between the variable R (return rate in percent of financial investment) and the variable t (age in years of the investment) given by the regression equation R = 2.5t + 5.3.

1- Without further information, can we assume there is a cause-and-effect relationship between the return rate and the age of the investment?

2- If the investment continues to grow at a constant rate, what is the expected return rate when the investment is 7 years old?

3-If the investment continues to grow at a constant rate, how old is the investment when the return rate is 32.8%?