A portfolio is composed of two stocks, A and B. Stock A has a standard deviation of return of 25%, while stock B has a standard deviation of return of 19%. Stock A comprises 70% of the portfolio, while stock B comprises 30% of the portfolio. If the variance of return on the portfolio is 0.045, the correlation coefficient between the returns on A and B is ___.

Please explain the algebra in this; otherwise don't answer it.